LearnDataStructuresandAlgorithmswithGolang

LevelupyourGoprogrammingskillstodevelopfasterandmoreefficientcodeBhagvanKommadi

BIRMINGHAM-MUMBAI

LearnDataStructuresandAlgorithmswithGolang

Copyright©2019PacktPublishingAllrightsreserved.Nopartofthisbookmaybereproduced,storedinaretrievalsystem,ortransmittedinanyformorbyanymeans,withoutthepriorwrittenpermissionofthepublisher,exceptinthecaseofbriefquotationsembeddedincriticalarticlesorreviews.Everyefforthasbeenmadeinthepreparationofthisbooktoensuretheaccuracyoftheinformationpresented.However,theinformationcontainedinthisbookissoldwithoutwarranty,eitherexpressorimplied.Neithertheauthor,norPacktPublishingoritsdealersanddistributors,willbeheldliableforanydamagescausedorallegedtohavebeencauseddirectlyorindirectlybythisbook.PacktPublishinghasendeavoredtoprovidetrademarkinformationaboutallofthecompaniesandproductsmentionedinthisbookbytheappropriateuseofcapitals.However,PacktPublishingcannotguaranteetheaccuracyofthisinformation.CommissioningEditor:RichaTripathiAcquisitionEditor:ShahnishKhanContentDevelopmentEditor:ZeeyanPinheiroTechnicalEditor:KetanKambleCopyEditor:SafisEditingProjectCoordinator:VaidehiSawantProofreader: SafisEditingIndexer:TejalDaruwaleSoniGraphics:AlishonMendonsaProductionCoordinator:DeepikaNaik

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Contributors

AbouttheauthorBhagvanKommadi,thefounderofQuanticaComputacaoandArchitectCorner,hasaround18years'experienceintheindustry,rangingfromlarge-scaleenterprisedevelopmenttoincubatingsoftwareproductstartups.Hehasamaster'sdegreeinIndustrialSystemsEngineeringfromtheGeorgiaInstituteofTechnology(1997)andabachelor'sdegreeinAerospaceEngineeringfromtheIITMadras(1993). HeisamemberoftheIFXforumandanindividualmemberofOracleJCP.HehasdevelopedGo-basedblockchainsolutionsintheretail,education,banking,andfinancialservicesectors.Hehasexperienceofbuildinghigh-transactionalapplicationsusingJava,Python,Go,Ruby,andJavaScriptframeworks.

AboutthereviewerEduardBondarenkoisasoftwaredeveloperlivinginKiev,Ukraine.HestartedprogrammingusingBasiconaZXSpectrummany,manyyearsago.Later,heworkedinthewebdevelopmentdomain.HehasusedRubyonRailsforover8years.HavingusedRubyforalongtime,hediscoveredClojureinearly2009,andlikedthesimplicityofthelanguage.BesidesRubyandClojure,heisinterestedinGoandReasonMLdevelopment.Iwanttothankmywonderfulwife,mychildren,andmyparentsforallthelove,support,andhelptheyhavegivenme.

WhatthisbookcoversChapter1,DataStructuresandAlgorithms,focusesonthedefinitionofabstractdatatypes,classifyingdatastructuresintolinear,non-linear,homogeneous,heterogeneous,anddynamictypes.Abstractdatatypes,suchascontainer,list,set,map,graph,stack,andqueue,arepresentedinthischapter.Thischapteralsocoverstheperformanceanalysisofdatastructures,aswellasthecorrectchoiceofdatastructuresandstructuraldesignpatterns.Chapter2,GettingStartedwithGoforDataStructuresandAlgorithms,coversGo-specificdatastructures,suchasarrays,slices,two-dimensionalslices,maps,structs,andchannels.Variadicfunctions,deferredfunctioncalls,andpanicandrecoveroperationsareintroduced.Slicingoperations,suchasenlargingusingappendandcopy,assigningparts,appendingaslice,andappendingpartofaslice,arealsopresentedinthischapter.Chapter3,LinearDataStructures,coverslineardatastructuressuchaslists,sets,tuples,stacks,andheaps.Theoperationsrelatedtothesetypes,includinginsertion,deletion,updating,reversing,andmergingareshownwithvariouscodesamples.Inthischapter,wepresentthecomplexityanalysisofvariousdatastructureoperationsthatdisplayaccessing,search,insertion,anddeletiontimes.Chapter4,Non-LinearDataStructures,coversnon-lineardatastructures,suchastrees,tables,containers,andhashfunctions.Treetypes,includingbinarytree,binarysearchtree,T-tree,treap,symboltable,B-tree,andB+tree,areexplainedwithcodeexamplesandcomplexityanalysis.Hashfunctiondatastructuresarepresented,alongwithexamplesincryptographyforavarietyofscenarios,suchasopenaddressing,linearprobing,universalhashing,anddoublehashing.Chapter5,HomogeneousDataStructures,covershomogeneousdatastructuressuchastwo-dimensionalandmulti-dimensionalarrays.Arrayshapes,types,literals,printing,construction,indexing,modification,transformation,andviewsarepresentedtogetherwithcodeexamplesandperformanceanalysis.Matrixrepresentation,multiplication,addition,subtraction,inversion,andtransposescenariosareshowntodemonstratetheusageofmulti-dimensionalarrays.Chapter6,HeterogeneousDataStructures,coversheterogeneousdatastructures,suchaslinkedlists,ordered,andunorderedlists.Wepresentthesinglylinkedlist,doublylinkedlist,andcircularlinkedlist,alongwithcodesamplesandefficiencyanalysis.OrderedandunorderedlistsfromHTML3.0areshowntodemonstratetheusageoflistsandstoragemanagement.

Chapter7,DynamicDataStructures,coversdynamicdatastructures,suchasdictionaries,TreeSets,andsequences.SynchronizedTreeSetsandmutableTreeSetsarecoveredinthischapteralongwithGocodeexhibits.SequencetypesincludingFarey,Fibonacci,look-and-say,andThue-Morse,arediscussedwithGoprograms.Thischapteralsoexplainstheusageanti-patternsofdictionaries,TreeSets,andsequences.Chapter8,ClassicAlgorithms,coverspre-order,post-order,in-order,level-ordertreetraversalsandlinkedlisttraversals.Sortingalgorithms,suchasbubble,selection,insertion,shell,merge,andquickareexplainedwithcodeexhibits.Searchalgorithms,aswellaslinear,sequential,binary,andinterpolationmethods,arealsocoveredinthischapter.Recursionandhashingareshownbymeansofcodesamples.Chapter9,NetworkandSparseMatrixRepresentation,coversdatastructuressuchasgraphsandlistsoflists.Differentusecasesfromreal-lifeapplications,suchassocialnetworkrepresentation,maplayouts,andknowledgecatalogs,areshownwithcodeexamplesandefficiencyanalysis. Chapter10,MemoryManagement,coversdynamicdatastructures,suchasAVLtreesandstackframes.Garbagecollection,cachemanagement,andspaceallocationalgorithmsarepresentedwithcodesamplesandefficiencyanalysis.Garbagecollectionalgorithms,suchassimple/deferred/one-bit/weightedreferencecounting,markandsweep,andgenerationalcollection,areexplainedwithananalysisoftheiradvantagesanddisadvantages.Appendix,NextSteps,shares thelearningoutcomesforthereaderarisingfromthebook.Thecoderepositorylinksandkeytakeawaysarepresented.Referencesareincludedforthelatestdatastructuresandalgorithms.Tipsandtechniquesareprovidedtokeepyourselfupdatedwiththelatestondatastructuresandalgorithms.

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TableofContentsTitlePageCopyrightandCredits

LearnDataStructuresandAlgorithmswithGolangAboutPackt

Whysubscribe?Packt.com

ContributorsAbouttheauthorAboutthereviewerPacktissearchingforauthorslikeyou

PrefaceWhothisbookisforWhatthisbookcoversTogetthemostoutofthisbook

DownloadtheexamplecodefilesDownloadthecolorimagesConventionsused

GetintouchReviews

6. Section1:IntroductiontoDataStructuresandAlgorithmsandtheGoLanguage

7. DataStructuresandAlgorithmsTechnicalrequirementsClassificationofdatastructuresandstructuraldesignpatterns

ClassificationofdatastructuresListsTuplesHeaps

StructuraldesignpatternsAdapterBridge

drawShapemethoddrawContourmethod

CompositeDecoratorFacadeFlyweightPrivateclassdataProxy

RepresentationofalgorithmsFlowchart

PseudocodeComplexityandperformanceanalysis

ComplexityanalysisofalgorithmsBigOnotationLinearcomplexityQuadraticcomplexityCubiccomplexityLogarithmiccomplexity

BruteforcealgorithmsDivideandconqueralgorithmsBacktrackingalgorithmsSummaryQuestionsandexercisesFurtherreading

8. GettingStartedwithGoforDataStructuresandAlgorithmsTechnicalrequirementsArraysSlices

Thelenfunction Slicefunction

Two-dimensionalslicesMapsDatabaseoperations

TheGetCustomermethodTheInsertCustomermethod

VariadicfunctionsTheupdateoperationThedeleteoperation

CRUDwebformsThedeferandpanicstatements

TheInsertCustomermethodTheUpdateCustomermethodTheDeleteCustomermethod

CRMwebapplicationTheCreatefunctionTheInsertfunctionTheAlterfunctionTheUpdatefunctionTheDeletefunctionThemainmethod

TheHeadertemplateTheFootertemplateTheMenutemplateTheCreatetemplate

TheUpdatetemplateTheViewtemplate

SummaryQuestionsFurtherreading

9. Section2:BasicDataStructuresandAlgorithmsusingGo10. LinearDataStructures

TechnicalrequirementsLists

LinkedListTheNodeclassTheLinkedListclass

TheAddToHeadmethodTheIterateListmethodTheLastNodemethodTheAddToEndmethodTheNodeWithValuemethodTheAddAftermethodThemainmethod

DoublylinkedlistTheNodeBetweenValuesmethodTheAddToHeadmethodAddAftermethodTheAddToEndmethodThemainmethod

SetsTheAddElementmethodTheDeleteElementmethodTheContainsElementmethodThemainmethod–containselementTheInterSectmethodTheUnionmethodThemainmethod–intersectionandunion

TuplesQueues

TheNewmethodTheAddmethodThemainmethod–queuesSynchronizedqueue

TheNewmethodTheStartTicketIssuemethod TheEndTicketIssuemethodTheticketIssuemethodTheStartPassmethod

TheEndPassmethodThepassengermethodThemainmethod

StacksTheNewmethodThePushmethodThePopmethodThemainmethod

SummaryQuestionsFurtherreading

11. Non-LinearDataStructuresTechnicalrequirementsTrees

BinarysearchtreeTheBinarySearchTreeclass

TheInsertElementmethodTheinsertTreeNodemethodTheinOrderTraversemethodTheinOrderTraverseTreemethodThePreOrderTraverseTreemethodThepreOrderTraverseTreemethodThePostOrderTraverseTreemethodThepostOrderTraverseTreemethodTheMinNodemethodTheMaxNodemethodTheSearchNodemethodThesearchNodemethodTheRemoveNodemethodTheremoveNodemethodTheStringmethodThestringifymethodThemainmethod

Adelson,Velski,andLandis(AVL)treeTheKeyValueinterfaceTheTreeNodeclass

TheoppositemethodThesingleRotationmethodThedoubleRotationmethodTheadjustBalancemethodTheBalanceTreemethodTheinsertRNodemethodTheInsertNodemethodTheRemoveNodemethod

TheremoveBalancemethodTheremoveRNodemethodThemainmethod

B+treeB-treeT-tree

TablesTheTableclassTheRowclassTheColumnclassTheprintTablemethodThemainmethod

SymboltablesContainers

CircularlinkedlistThehashfunctionsSummaryQuestionsFurtherreading

12. HomogeneousDataStructuresTechnicalrequirementsTwo-dimensionalarrays

RowmatrixColumnmatrixLowertriangularmatrixUppertriangularmatrixNullmatrixIdentitymatrixSymmetricmatrixBasic2Dmatrixoperations

TheaddmethodThesubtractmethodThemultiplymethodThetransposemethodThedeterminantmethodTheinversemethod

Zig-zagmatrixSpiralmatrixBooleanmatrix

TheprintMatrix methodThemainmethod

Multi-dimensionalarraysTensors

Summary

QuestionsFurtherreading

13. HeterogeneousDataStructuresTechnicalrequirementsLinkedlists

SinglylinkedlistsTheCreateLinkedListmethodTheReverseLinkedListmethodThemainmethod

DoublylinkedlistsCircular-linkedlists

TheCircularQueueclassTheNewQueuemethodTheIsUnUsedmethodTheIsCompletemethodTheAddmethodTheMoveOneStepmethodThemainmethod

OrderedlistsTheToStringmethodTheSortByAgetypeTheThingclass

TheByFactorfunctiontypeTheSortmethod

ThingsorterclassThelen,swap,andlessmethodsThemainmethod

ThestructtypeThemultiSorterclass

TheSortmethodTheOrderBymethodThelenmethodTheSwapmethodThelessmethodThemainmethod

UnorderedlistsTheUnOrderedListclass

TheAddtoHeadmethodTheIterateListmethodThemainmethod

SummaryQuestionsFurtherreading

14. DynamicDataStructures

TechnicalrequirementsDictionaries

DictValtypeDictionaryclass

PutmethodRemovemethodContainsmethodFindmethodResetmethodNumberOfElementsmethodGetKeysmethodGetValuesmethodThemainmethod

TreeSetsInsertTreeNodemethodDeletemethodInOrderTraverseTreemethodTheinOrderTraverseTreemethodPreOrderTraverseTreemethodThepreOrderTraverseTreemethodSearchmethodTheStringmethodThemainmethodSynchronizedTreeSetsMutable TreeSets

RemoveNodemethodTreeset.bst

SequencesFareysequence

StringmethodTheg methodThemainmethod

FibonaccisequenceFibonacciNumbermethodMainmethod

Look-and-sayThue–Morse

SummaryQuestionsFurtherreading

15. ClassicAlgorithmsTechnicalrequirementsSorting

Bubble

SelectionTheswapmethodThemainmethod

InsertionInsertionSortermethodThemainmethod

ShellThepowermethodThemainmethod

MergeMergeSortermethodJoinArraysmethodThemainmethod

QuickThedividePartsmethodTheswapmethodThemainmethod

SearchingLinearBinaryInterpolation

RecursionHashing

TheCreateHashMutliplemethodThe XORmethodThemainmethod

SummaryQuestionsFurtherreading

16. Section3:AdvancedDataStructuresandAlgorithmsusingGo17. NetworkandSparseMatrixRepresentation

TechnicalrequirementsNetworkrepresentationusinggraphs

TheLinkclassTheNewSocialGraphmethodTheAddLinkmethodThePrintLinksmethodThemainmethodTest

RepresentingasocialnetworkTheNewSocialGraphmethodTheAddEntitymethodTheAddLinkmethodThePrintLinksmethod

ThemainmethodMaplayouts

TheMapLayoutclassTheNewMapLayoutmethodTheAddPlacemethodTheAddLinkmethod ThePrintLinksmethodThemainmethodTest

KnowledgegraphsTheKnowledgeGraphclass

TheNewKnowledgeGraphmethodTheAddClassmethodTheAddLinkmethodThePrintLinksmethodThemainmethodTest

SparsematrixrepresentationusingalistoflistsSparseMatrixclass

TheShapemethodTheNumNonZeromethodTheLessThanmethodTheEqualmethodTheGetValuemethodTheSetValuemethodTheNewSparseMatrixmethodThemainmethod

SummaryQuestionsFurtherreading

18. MemoryManagementTechnicalrequirementsGarbagecollection

TheReferenceCounterclassThenewReferenceCountermethod

TheStackclassTheStackclass–anewmethodThemainmethod

ReferencecountingSimplereferencecountingDeferredreferencecountingOne-bitreferencecountingWeightedreferencecounting

Themark-and-sweepalgorithm

ThegenerationalcollectionalgorithmCachemanagement

TheCacheObjectclassTheIfExpiredmethod

TheCacheclassTheNewCachemethodTheGetObjectmethodTheSetValuemethod

ThemainmethodSpaceallocation

PointersTheaddOnemethodThemainmethod

Concepts– GomemorymanagementProfiling

SummaryQuestionsFurtherreading

NextStepsTechnicalrequirementsLearningoutcomes

KeytakeawaysNextsteps

Chapter1–DataStructuresandAlgorithmsChapter2–GettingStartedwithGoforDataStructures and AlgorithmsChapter3–LinearDataStructuresChapter4–Non-LinearDataStructuresChapter5–HomogeneousDataStructuresChapter6–HeterogeneousDataStructuresChapter7–Dynamic DataStructuresChapter8– ClassicAlgorithmsChapter9–NetworkandSparseMatrixRepresentationChapter10–MemoryManagement

TipsandtechniquesUsingchannelwithatimeoutintervalUsingcontextinsteadofchannelLoggingwiththelinenumberGotoolusageGoenvironmentvariablesTesttableImportingpackagesPanic,defer,andrecover

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PrefaceLearnDataStructuresandAlgorithmswithGocoverstopicsrelatedtosimpleandadvancedconceptsincomputerprogramming.Theprimaryobjectiveistochoosethecorrectalgorithmanddatastructuresforaproblem.Thisbookexplainstheconceptsforcomparingalgorithmcomplexityanddatastructuresintermsofcodeperformanceandefficiency.Golanghasbeenthebuzzwordforthelasttwoyears,withtremendousimprovementsbeingseeninthisarea.ManydevelopersandorganizationsareslowlymigratingtoGolang,adoptingitsfast,lightweight,andinbuiltconcurrencyfeatures.Thismeansweneedtohaveasolidfoundationindatastructuresandalgorithmswiththisgrowinglanguage.

WhothisbookisforThiscomprehensivebookisfordeveloperswhowanttounderstandhowtoselectthebestdatastructuresandalgorithmsthatwillhelptosolvespecificproblems.SomebasicknowledgeofGoprogrammingwouldbeanaddedadvantage.Thisbookisforanyonewhowantstolearnhowtowriteefficientprogramsandusetheproperdatastructuresandalgorithms.

TogetthemostoutofthisbookTheknowledgeweassumeisbasicprogramminginalanguageandmathematicalskillsrelatedtotopicsincludingmatrices,setoperations,andstatisticalconcepts.Thereadershouldhavetheabilitytowritepseudocodebasedonaflowchartoraspecifiedalgorithm.Writingfunctionalcode,testing,followingguidelines,andbuildingacomplexprojectintheGolanguagearetheprerequisitesthatweassumeintermsofreaderskills.

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DownloadthecolorimagesWealsoprovideaPDFfilethathascolorimagesofthescreenshots/diagramsusedinthisbook.Youcandownloadithere:http://www.packtpub.com/sites/default/files/downloads/9781789618501_ColorImages.pdf.

Conventionsused

Thereareanumberoftextconventionsusedthroughoutthisbook.CodeInText:Indicatescodewordsintext,databasetablenames,foldernames,filenames,fileextensions,pathnames,dummyURLs,userinput,andTwitterhandles.Hereisanexample:"Let'stakealookatthe len functioninthenextsection."Ablockofcodeissetasfollows:

//mainpackagehasexamplesshown//inHands-OnDataStructuresandalgorithmswithGobookpackagemain

//importingfmtpackageimport("fmt")//mainmethodfuncmain(){fmt.Println("HelloWorld")}

Anycommand-lineinputoroutputiswrittenasfollows:gobuild

./hello_world

Bold:Indicatesanewterm,animportantword,orwordsthatyouseeonscreen.

Warningsorimportantnotesappearlikethis.Tipsandtricksappearlikethis.

Getintouch

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Section1:IntroductiontoDataStructuresandAlgorithmsandtheGoLanguageWewillbeintroducingtheabstractdatatypes,definition,andclassificationofdatastructures.Readerswillbewell-versedwithperformanceanalysisofalgorithmsandchoosingappropriatedatastructuresforstructuraldesignpatternsafterreadingthispart.Thissectioncontainsthefollowingchapters:

Chapter1,DataStructuresandAlgorithmsChapter2, GettingStartedwithGoforDataStructuresandAlgorithms

DataStructuresandAlgorithmsAdatastructureistheorganizationofdatatoreducethestoragespaceusedandtoreducethedifficultywhileperformingdifferenttasks.Datastructuresareusedtohandleandworkwithlargeamountsofdatainvariousfields,suchasdatabasemanagementandinternetindexingservices.Inthischapter,wewillfocusonthedefinitionofabstractdatatypes,classifyingdatastructuresintolinear,nonlinear,homogeneous,heterogeneous,anddynamictypes.Abstractdatatypes,suchas Container,List,Set,Map,Graph,Stack,andQueue, arepresentedinthischapter. We willalsocovertheperformanceanalysisofdatastructures,choosingtherightdatastructures,andstructuraldesignpatterns.ThereadercanstartwritingbasicalgorithmsusingtherightdatastructuresinGo. Givenaproblem,choosingthedatastructureanddifferentalgorithmswillbethefirststep.Afterthis,doingperformanceanalysisisthenextstep.Timeandspaceanalysisfordifferentalgorithmshelpscomparethemandhelpsyouchoosetheoptimalone. ItisessentialtohavebasicknowledgeofGotogetstarted.Inthischapter,wewillcoverthefollowingtopics:

ClassificationofdatastructuresandstructuraldesignpatternsRepresentationofalgorithmsComplexityandperformanceanalysisBruteforcealgorithmsDivideandconqueralgorithmsBacktrackingalgorithms

TechnicalrequirementsInstallGoversion1.10from https://golang.org/doc/install foryouroperatingsystem. ThecodefilesforthischaptercanbefoundatthefollowingGitHubURL: https://github.com/PacktPublishing/Learn-Data-Structures-and-Algorithms-with-Golang/tree/master/Chapter01.ChecktheinstallationofGobyrunningthehelloworldprogram athttps://github.com/PacktPublishing/Learn-Data-Structures-and-Algorithms-with-Golang/tree/master/hello_world:

//mainpackagehasexamplesshown//inHands-OnDataStructuresandalgorithmswithGobookpackagemain

//importingfmtpackageimport("fmt")//mainmethodfuncmain(){fmt.Println("HelloWorld")}

Runthefollowingcommands:gobuild

./hello_world

Thefollowingscreenshotdisplaystheoutput:

Let'stakealookattheclassificationofdatastructuresandstructuraldesignpatternsinthenextsection.

ClassificationofdatastructuresandstructuraldesignpatternsYoucanchooseadatastructurebyusingclassification. Inthissection,wediscussdatastructureclassificationindetail.Thedesignpatternsrelatedtothedatastructurearecoveredaftertheclassification.Inthenextsection,we'lltakealookatclassificationofdatastructures.

ClassificationofdatastructuresThetermdatastructurereferstotheorganizationofdatainacomputer'smemory,inordertoretrieveitquicklyforprocessing.Itisaschemefordataorganizationtodecouplethefunctionaldefinitionofadatastructurefromitsimplementation.Adatastructureischosenbasedontheproblemtypeandtheoperationsperformedonthedata.Ifthesituationrequiresvariousdatatypeswithinadatastructure,wecanchooseheterogeneousdatastructures. Linked,ordered,andunorderedlistsaregroupedasheterogeneousdatastructures. Lineardatastructuresarelists,sets,tuples,queues,stacks,andheaps.Trees,tables,andcontainersarecategorizedasnonlineardatastructures.Two-dimensionalandmultidimensionalarraysaregroupedashomogeneousdatastructures.Dynamicdatastructuresaredictionaries,treesets,andsequences.TheclassificationofDataStructuresisshowinthefollowingdiagram:

Let'stakealookatlists,tuplesandheapsinthenextsections.

ListsAlistisasequenceofelements.Eachelementcanbeconnectedtoanotherwithalinkinaforwardorbackwarddirection.Theelementcanhaveotherpayloadproperties.Thisdatastructureisabasictypeofcontainer.Listshaveavariablelengthanddevelopercanremoveoraddelementsmore easilythananarray.Dataitemswithinalistneednotbecontiguousinmemoryorondisk.Linkedlistswereproposedby AllenNewell,CliffShaw,andHerbertA.SimonatRANDCorporation.Togetstarted,alistcanbeusedinGo,asshowninthefollowingexample;elementsareaddedthroughthe PushBackmethodonthelist,whichisinthe container/listpackage:

//mainpackagehasexamplesshown//inHands-OnDataStructuresandalgorithmswithGobookpackagemain

//importingfmtandcontainerlistpackagesimport("fmt""container/list")

//mainmethodfuncmain(){varintListlist.ListintList.PushBack(11)intList.PushBack(23)intList.PushBack(34)

forelement:=intList.Front();element!=nil;element=element.Next(){fmt.Println(element.Value.(int))}}

Thelistisiteratedthroughthe forloop,andtheelement'svalueisaccessedthroughtheValuemethod.Runthefollowingcommands:

gorunlist.go

Thefollowingscreenshotdisplaystheoutput:

Let'stakealookatTuplesinthenextsection.

TuplesAtupleisafinitesortedlistofelements.It isadatastructurethatgroupsdata. Tuplesaretypicallyimmutablesequentialcollections.Theelementhasrelatedfieldsofdifferentdatatypes.Theonlywaytomodifyatupleistochangethefields.Operatorssuchas+and*canbeappliedtotuples.Adatabaserecordisreferredtoasatuple.Inthefollowingexample,powerseriesofintegersarecalculatedandthesquareandcubeoftheintegerisreturnedasatuple:

//mainpackagehasexamplesshown//inHands-OnDataStructuresandalgorithmswithGobookpackagemain

//importingfmtpackageimport("fmt"

)//getsthepowerseriesofintegeraandreturnstupleofsquareofa//andcubeofafuncpowerSeries(aint)(int,int){

returna*a,a*a*a

}

ThemainmethodcallsthepowerSeriesmethodwith3asaparameter. Thesquareandcube valuesarereturnedfromthemethod:

//mainmethodfuncmain(){

varsquareintvarcubeintsquare,cube=powerSeries(3)

fmt.Println("Square",square,"Cube",cube)

}

Runthefollowingcommands:goruntuples.go

Thefollowingscreenshotdisplaystheoutput:

ThetuplescanbenamedinthepowerSeriesfunction,asshowninthefollowingcode:

funcpowerSeries(aint)(squareint,cubeint){

square=a*a

cube=square*a

return

}

Ifthereisanerror,itcanbepassedwithtuples,asshowninthefollowingcode:

funcpowerSeries(aint)(int,int,error){

square=a*a

cube=square*a

returnsquare,cube,nil

}

HeapsAheapisadatastructurethatisbasedontheheapproperty.Theheapdatastructureisusedinselection,graph,andk-waymergealgorithms.Operationssuchasfinding,merging,insertion,keychanges,anddeletingareperformedonheaps.Heapsarepartofthe container/heap packageinGo.Accordingtotheheaporder(maximumheap)property,thevaluestoredateachnodeisgreaterthanorequaltoitschildren.Iftheorderisdescending,itisreferredtoasamaximumheap;otherwise,it'saminimumheap.TheheapdatastructurewasproposedbyJ.W.J.Williamsin1964foraheapsortingalgorithm.Itisnotasorteddatastructure,butpartiallyordered.Thefollowingexampleshowshowtousethecontainer/heappackagetocreateaheapdatastructure:

//mainpackagehasexamplesshown//inHands-OnDataStructuresandalgorithmswithGobookpackagemain

//importingfmtpackageandcontainer/heapimport("container/heap""fmt")//integerHeapatypetypeIntegerHeap[]int

//IntegerHeapmethod-getsthelengthofintegerHeapfunc(iheapIntegerHeap)Len()int{returnlen(iheap)}

//IntegerHeapmethod-checksifelementofiindexislessthanjindexfunc(iheapIntegerHeap)Less(i,jint)bool{returniheap[i]<iheap[j]}//IntegerHeapmethod-swapstheelementofitojindexfunc(iheapIntegerHeap)Swap(i,jint){iheap[i],iheap[j]=iheap[j],iheap[i]}

IntegerHeaphasaPushmethodthatpushestheitemwiththeinterface://IntegerHeapmethod-pushestheitemfunc(iheap*IntegerHeap)Push(heapintfinterface{}){

*iheap=append(*iheap,heapintf.(int))}//IntegerHeapmethod-popstheitemfromtheheapfunc(iheap*IntegerHeap)Pop()interface{}{

func(iheap*IntegerHeap)Pop()interface{}{

varnintvarx1intvarpreviousIntegerHeap=*iheapn=len(previous)x1=previous[n-1]*iheap=previous[0:n-1]returnx1}

//mainmethodfuncmain(){varintHeap*IntegerHeap=&IntegerHeap{1,4,5}

heap.Init(intHeap)heap.Push(intHeap,2)fmt.Printf("minimum:%d\n",(*intHeap)[0])forintHeap.Len()>0{fmt.Printf("%d\n",heap.Pop(intHeap))}}

Runthefollowingcommands:gorunheap.go

Thefollowingscreenshotdisplaystheoutput:

Let'stakealookatstructuraldesignpatternsinthenextsection

StructuraldesignpatternsStructuraldesignpatternsdescribetherelationshipsbetweentheentities.Theyareusedtoformlargestructuresusingclassesandobjects.Thesepatternsareusedtocreateasystemwithdifferentsystemblocksinaflexiblemanner. Adapter,bridge,composite,decorator,facade,flyweight,privateclassdata,andproxyaretheGangofFour(GoF)structuraldesignpatterns. Theprivateclassdatadesignpatternistheotherdesignpatterncoveredinthissection.Wewilltakealookatadapterandbridgedesignpatternsinthenextsections.

AdapterTheadapterpatternprovidesawrapperwithaninterfacerequiredbytheAPIclienttolinkincompatibletypesandactasatranslatorbetweenthetwotypes.Theadapterusestheinterfaceofaclasstobeaclasswithanothercompatibleinterface.Whenrequirementschange,therearescenarioswhereclassfunctionalityneedstobechangedbecauseofincompatibleinterfaces.Thedependencyinversionprinciplecanbeadheredtobyusingtheadapterpattern,whenaclassdefinesitsowninterfacetothenextlevelmoduleinterfaceimplementedbyanadapterclass.Delegationistheotherprincipleusedbytheadapterpattern.Multipleformatshandlingsource-to-destinationtransformationsarethescenarioswheretheadapterpatternisapplied.Theadapterpatterncomprisesthetarget,adaptee,adapter,andclient:

Targetistheinterfacethattheclientcallsandinvokesmethodsontheadapterandadaptee.Theclientwantstheincompatibleinterfaceimplementedbytheadapter.Theadaptertranslatestheincompatibleinterfaceoftheadapteeintoaninterfacethattheclientwants.

Let'ssayyouhavean IProcessor interfacewithaprocessmethod,the Adapter classimplementstheprocessmethodandhasan Adaptee instanceasanattribute.TheAdapteeclasshasaconvertmethodandan adapterTypeinstancevariable.ThedeveloperwhileusingtheAPIclientcallstheprocessinterfacemethod toinvokeconvertonAdaptee.Thecodeisasfollows:

//mainpackagehasexamplesshown//inHands-OnDataStructuresandalgorithmswithGobookpackagemain//importingfmtpackageimport("fmt")//IProcessinterfacetypeIProcessinterface{process()}//AdapterstructtypeAdapterstruct{adapteeAdaptee}

TheAdapterclasshasa process methodthatinvokesthe convertmethodonadaptee:

//Adapterclassmethodprocessfunc(adapterAdapter)process(){fmt.Println("Adapterprocess")adapter.adaptee.convert()}//AdapteeStructtypeAdapteestruct{adapterTypeint}//Adapteeclassmethodconvertfunc(adapteeAdaptee)convert(){fmt.Println("Adapteeconvertmethod")}//mainmethodfuncmain(){varprocessorIProcess=Adapter{}processor.process()}

Runthefollowingcommands:gorunadapter.go

Thefollowingscreenshotdisplaystheoutput:

Let'stakealookatBridgepatterninthenextsection.

BridgeBridgedecouplestheimplementationfromtheabstraction.Theabstractbaseclasscanbesubclassedtoprovidedifferentimplementationsandallowimplementationdetailstobemodifiedeasily.Theinterface,whichisabridge,helpsinmakingthefunctionalityofconcreteclassesindependentfromtheinterfaceimplementerclasses.Thebridgepatternsallowtheimplementationdetailstochangeatruntime.Thebridgepatterndemonstratestheprinciple,preferringcompositionoverinheritance.Ithelpsinsituationswhereoneshouldsubclassmultipletimesorthogonaltoeachother.Runtimebindingoftheapplication,mappingoforthogonalclasshierarchies,andplatformindependenceimplementationarethescenarioswherethebridgepatterncanbeapplied.Thebridgepatterncomponentsareabstraction,refinedabstraction,implementer,andconcreteimplementer.Abstractionistheinterfaceimplementedasanabstractclassthatclientsinvokewith themethodontheconcreteimplementer.Abstractionmaintainsahas-a relationshipwiththeimplementation,insteadofan is-a relationship.Thehas-a relationshipismaintainedbycomposition.Abstractionhasareferenceoftheimplementation.Refinedabstractionprovidesmorevariationsthanabstraction.Let'ssayIDrawShapeisaninterfacewiththe drawShape method.  DrawShapeimplementstheIDrawShapeinterface.Wecreatean IContourbridgeinterface withthe drawContour method.Thecontourclassimplementsthe IContourinterface.Theellipseclasswillhavea,b,rpropertiesanddrawShape(aninstanceofDrawShape).Theellipseclassimplementsthe contour bridgeinterfacetoimplementthe drawContour method.The  drawContour methodcallsthe drawShape methodonthe drawShape instance.Thefollowingcodedemonstratesthebridgeimplementation: 

//mainpackagehasexamplesshown//inHands-OnDataStructuresandalgorithmswithGobookpackagemain//importingfmtpackageimport("fmt")//IDrawShapeinterfacetypeIDrawShapeinterface{drawShape(x[5]float32,y[5]float32)}//DrawShapestruct

//DrawShapestruct

typeDrawShapestruct{}

drawShapemethod

ThedrawShapemethoddrawstheshapegiventhecoordinates,asshowninthefollowingcode:

//DrawShapestructhasmethoddrawShapewithfloatxandycoordinatesfunc(drawShapeDrawShape)drawShape(x[5]float32,y[5]float32){fmt.Println("DrawingShape")}//IContourinteracetypeIContourinterface{drawContour(x[5]float32,y[5]float32)resizeByFactor(factorint)}//DrawContourstructtypeDrawContourstruct{x[5]float32y[5]float32shapeDrawShapefactorint}

drawContourmethod

The drawContourmethod ofthe DrawContour classcallsthe drawShape methodontheshapeinstance,thisisshowninthefollowingcode:

//DrawContourmethoddrawContourgiventhecoordinatesfunc(contourDrawContour)drawContour(x[5]float32,y[5]float32){fmt.Println("DrawingContour")contour.shape.drawShape(contour.x,contour.y)}//DrawContourmethodresizeByFactorgivenfactorfunc(contourDrawContour)resizeByFactor(factorint){contour.factor=factor}//mainmethodfuncmain(){varx=[5]float32{1,2,3,4,5}vary=[5]float32{1,2,3,4,5}varcontourIContour=DrawContour{x,y,DrawShape{},2}contour.drawContour(x,y)contour.resizeByFactor(2)}

Runthefollowingcommands:gorunbridge.go

Thefollowingscreenshotdisplaystheoutput:

WewilltakealookatComposite,Decorator,FacadeandFlyweightdesignpatternsinthenextsections.

CompositeAcompositeisagroupofsimilarobjectsinasingleobject.Objectsarestoredinatreeformtopersistthewholehierarchy.Thecompositepatternisusedtochangeahierarchicalcollectionofobjects.The compositepatternismodeledonaheterogeneouscollection.Newtypesofobjectscanbeaddedwithoutchangingtheinterfaceandtheclientcode.Youcanusethecompositepattern,forexample,forUIlayoutsontheweb,fordirectorytrees,andformanagingemployeesacrossdepartments.Thepatternprovidesamechanismtoaccesstheindividualobjectsandgroupsinasimilarmanner.Thecompositepatterncomprisesthecomponentinterface,componentclass,composite,andclient:

Thecomponentinterfacedefinesthedefaultbehaviorofallobjectsandbehaviorsforaccessingthecomponentsofthecomposite.Thecompositeandcomponentclassesimplementthecomponentinterface.Theclientinteractswiththecomponentinterfacetoinvokemethodsinthecomposite.

Let'ssaythereisan IComposite interfacewiththeperformmethodandBranchClass thatimplementsIComposite andhasthe addLeaf,addBranch,andperform methods.TheLeafletclassimplementsICompositewiththeperformmethod. BranchClasshasaone-to-manyrelationshipwithleafsandbranches.Iteratingoverthebranchrecursively,onecantraversethecompositetree,asshowninthefollowingcode:

//mainpackagehasexamplesshown//inHands-OnDataStructuresandalgorithmswithGobookpackagemain//importingfmtpackageimport("fmt")//ICompositeinterfacetypeICompositeinterface{perform()}//LeafletstructtypeLeafletstruct{namestring}//Leafletclassmethodperformfunc(leaf*Leaflet)perform(){fmt.Println("Leaflet"+leaf.name)}//BranchstructtypeBranchstruct{leafs[]Leaflet

leafs[]Leaflet

namestringbranches[]Branch}

The performmethodofthe Branch class callsthe perform methodonbranchandleafs,asseeninthecode:

//Branchclassmethodperformfunc(branch*Branch)perform(){fmt.Println("Branch:"+branch.name)for_,leaf:=rangebranch.leafs{leaf.perform()}for_,branch:=rangebranch.branches{branch.perform()}}//Branchclassmethodaddleafletfunc(branch*Branch)add(leafLeaflet){branch.leafs=append(branch.leafs,leaf)}

Asshowninthefollowingcode,the addBranchmethod ofthe Branch class addsanewbranch:

//BranchclassmethodaddBranchbranchfunc(branch*Branch)addBranch(newBranchBranch){branch.branches=append(branch.branches,newBranch)}//BranchclassmethodgetLeafletsfunc(branch*Branch)getLeaflets()[]Leaflet{returnbranch.leafs}//mainmethodfuncmain(){varbranch=&Branch{name:"branch1"}varleaf1=Leaflet{name:"leaf1"}varleaf2=Leaflet{name:"leaf2"}varbranch2=Branch{name:"branch2"}branch.add(leaf1)branch.add(leaf2)branch.addBranch(branch2)branch.perform()}

Runthefollowingcommands:goruncomposite.go

Thefollowingscreenshotdisplaystheoutput:

Let'stakealookatDecoratorpatterninthenextsection.

DecoratorInascenariowhereclassresponsibilitiesareremovedoradded,thedecoratorpatternisapplied.Thedecoratorpatternhelpswithsubclassingwhen modifyingfunctionality,insteadofstaticinheritance.Anobjectcanhavemultipledecoratorsandrun-timedecorators.Thesingleresponsibilityprinciplecanbeachievedusingadecorator. The decoratorcanbeappliedto windowcomponentsandgraphicalobjectmodeling.Thedecoratorpatternhelpswithmodifyingexistinginstanceattributesandaddingnewmethodsatrun-time.Thedecoratorpatternparticipantsarethecomponentinterface,theconcretecomponentclass,andthe decoratorclass:

Theconcretecomponentimplementsthecomponentinterface.Thedecoratorclassimplementsthecomponentinterfaceandprovidesadditionalfunctionalityinthesamemethodoradditionalmethods.Thedecoratorbasecanbeaparticipantrepresentingthebaseclassforalldecorators.

Let'ssayIProcessisaninterfacewiththeprocessmethod.ProcessClassimplementsaninterfacewiththeprocessmethod.ProcessDecoratorimplementstheprocessinterfaceandhasaninstanceofProcessClass.ProcessDecoratorcanaddmorefunctionalitythan ProcessClass,asshowninthefollowingcode:

//mainpackagehasexamplesshown//inHands-OnDataStructuresandalgorithmswithGobookpackagemain//importingfmtpackageimport("fmt")//IProcessInterfacetypeIProcessinterface{process()}//ProcessClassstructtypeProcessClassstruct{}//ProcessClassmethodprocessfunc(process*ProcessClass)process(){fmt.Println("ProcessClassprocess")}//ProcessDecoratorstructtypeProcessDecoratorstruct{processInstance*ProcessClass}

Inthefollowingcode,theProcessDecoratorclassprocessmethod invokestheprocessmethodonthedecoratorinstanceofProcessClass:

//ProcessDecoratorclassmethodprocessfunc(decorator*ProcessDecorator)process(){ifdecorator.processInstance==nil{fmt.Println("ProcessDecoratorprocess")}else{fmt.Printf("ProcessDecoratorprocessand")decorator.processInstance.process()}}//mainmethodfuncmain(){varprocess=&ProcessClass{}vardecorator=&ProcessDecorator{}decorator.process()decorator.processInstance=processdecorator.process()}

Runthefollowingcommands:gorundecorator.go

Thefollowingscreenshotdisplaystheoutput:

Let'stakealookatFacadepatterninthenextsection.

FacadeFacadeisusedtoabstractsubsysteminterfaceswithahelper.Thefacadedesignpatternisusedinscenarioswhenthenumberofinterfacesincreasesandthesystemgetscomplicated.Facadeisanentrypointtodifferentsubsystems,anditsimplifiesthedependenciesbetweenthesystems.Thefacadepatternprovidesaninterfacethathidestheimplementationdetailsofthehiddencode.Alooselycoupledprinciplecanberealizedwithafacadepattern.YoucanuseafacadetoimprovepoorlydesignedAPIs.InSOA,aservicefacadecanbeusedtoincorporatechangestothecontractandimplementation.The facadepatternismadeupofthe facadeclass,moduleclasses,andaclient:

Thefacadedelegatestherequestsfromtheclienttothemoduleclasses.Thefacadeclasshidesthecomplexitiesofthesubsystemlogicandrules.Moduleclassesimplementthebehaviorsandfunctionalitiesofthemodulesubsystem.Theclientinvokesthefacademethod.Thefacadeclassfunctionalitycanbespreadacrossmultiplepackagesandassemblies.

Forexample,account,customer,andtransactionaretheclassesthathaveaccount,customer,andtransactioncreationmethods.BranchManagerFacadecanbeusedbytheclienttocreateanaccount,customer,andtransaction:

//mainpackagehasexamplesshown//inHands-OnDataStructuresandalgorithmswithGobookpackagemain//importingfmtpackageimport("fmt")//AccountstructtypeAccountstruct{idstringaccountTypestring}//Accountclassmethodcreate-createsaccountgivenAccountTypefunc(account*Account)create(accountTypestring)*Account{fmt.Println("accountcreationwithtype")account.accountType=accountTypereturnaccount}//AccountclassmethodgetByIdgivenidstringfunc(account*Account)getById(idstring)*Account{fmt.Println("gettingaccountbyId")returnaccount

returnaccount

}

Theaccountclasshasthe deleteById method,whichisusedtodeleteanaccountwithagivenID,asshowninthefollowingcode:

//AccountclassmethoddeleteByIdgivenidstringfunc(account*Account)deleteById(idstring)(){fmt.Println("deleteaccountbyid")}//CustomerstructtypeCustomerstruct{namestringidint}

Inthefollowingcode,thecustomerclasshasamethodthatcreatesanewcustomerwithname:

//Customerclassmethodcreate-createCustomergivennamefunc(customer*Customer)create(namestring)*Customer{fmt.Println("creatingcustomer")customer.name=namereturncustomer}//TransactionstructtypeTransactionstruct{idstringamountfloat32srcAccountIdstringdestAccountIdstring}

Asshowninthefollowingcode,thetransactionclasshasthe create methodforcreatingatransaction:

//TransactionclassmethodcreateTransactionfunc(transaction*Transaction)create(srcAccountIdstring,destAccountIdstring,amountfloat32)*Transaction{fmt.Println("creatingtransaction")transaction.srcAccountId=srcAccountIdtransaction.destAccountId=destAccountIdtransaction.amount=amountreturntransaction}//BranchManagerFacadestructtypeBranchManagerFacadestruct{account*Accountcustomer*Customertransaction*Transaction}//methodNewBranchManagerFacadefuncNewBranchManagerFacade()*BranchManagerFacade{return&BranchManagerFacade{&Account{},&Customer{},&Transaction{}}}

BranchManagerFacadehasthe createCustomerAccount method,whichcallsthe createmethodonthe customerclassinstance,asshowninthefollowingcode:

//BranchManagerFacadeclassmethodcreateCustomerAccountfunc(facade*BranchManagerFacade)createCustomerAccount(customerNamestring,accountTypestring)(*Customer,*Account){varcustomer=facade.customer.create(customerName)varaccount=facade.account.create(accountType)returncustomer,account}//BranchManagerFacadeclassmethodcreateTransactionfunc(facade*BranchManagerFacade)createTransaction(srcAccountIdstring,destAccountIdstring,amountfloat32)*Transaction{vartransaction=facade.transaction.create(srcAccountId,destAccountId,amount)returntransaction}

ThemainmethodcallstheNewBranchManagerFacademethodtocreateafacade.Themethodsonfacadeareinvokedtocreatecustomerandaccount:

//mainmethodfuncmain(){varfacade=NewBranchManagerFacade()varcustomer*Customervaraccount*Accountcustomer,account=facade.createCustomerAccount("ThomasSmith","Savings")fmt.Println(customer.name)fmt.Println(account.accountType)vartransaction=facade.createTransaction("21456","87345",1000)fmt.Println(transaction.amount)}

Runthefollowingcommands:gorunfacade.go

Thefollowingscreenshotdisplaystheoutput:

Let'stakealookatFlyweightpatterninthenextsection.

FlyweightFlyweightisusedtomanagethestateofanobjectwithhighvariation.Thepatternallowsustosharecommonpartsoftheobjectstateamongmultipleobjects,insteadofeachobjectstoringit.Variableobjectdataisreferredtoasextrinsicstate,andtherestoftheobjectstateisintrinsic.Extrinsicdataispassedtoflyweightmethodsandwillneverbestoredwithinit.Flyweightpatternhelpsreducetheoverallmemoryusageandtheobjectinitializingoverhead.Thepatternhelpscreateinterclassrelationshipsandlowermemorytoamanageablelevel.Flyweightobjectsareimmutable.Valueobjectsareagoodexampleoftheflyweightpattern.Flyweightobjectscanbecreatedinasinglethreadmode,ensuringoneinstancepervalue.Inaconcurrentthreadscenario,multipleinstancesarecreated.Thisisbasedontheequalitycriterionofflyweightobjects.TheparticipantsoftheflyweightpatternaretheFlyWeightinterface,ConcreteFlyWeight,FlyWeightFactory,andthe Clientclasses:

TheFlyWeightinterfacehasamethodthroughwhichflyweightscangetandactontheextrinsicstate.ConcreteFlyWeightimplementstheFlyWeightinterfacetorepresentflyweightobjects.FlyweightFactoryisusedtocreateandmanageflyweightobjects.TheclientinvokesFlyweightFactorytogetaflyweightobject.UnsharedFlyWeightcanhaveafunctionalitythatisnotshared.Clientclasses

Let'ssayDataTransferObjectisaninterfacewiththe getIdmethod.DataTransferObjectFactorycreatesadatatransferobjectthroughgetDataTransferObjectbytheDTOtype.TheDTOtypesarecustomer,employee,manager,andaddress,asshowninthefollowingcode:

//mainpackagehasexamplesshown//inHands-OnDataStructuresandalgorithmswithGobookpackagemain//importingfmtpackageimport("fmt")//DataTransferObjectFactorystructtypeDataTransferObjectFactorystruct{poolmap[string]DataTransferObject}//DataTransferObjectFactoryclassmethodgetDataTransferObjectfunc(factoryDataTransferObjectFactory)getDataTransferObject(dtoTypestring)DataTransferObject{vardto=factory.pool[dtoType]

vardto=factory.pool[dtoType]

ifdto==nil{fmt.Println("newDTOofdtoType:"+dtoType)switchdtoType{case"customer":factory.pool[dtoType]=Customer{id:"1"}case"employee":factory.pool[dtoType]=Employee{id:"2"}case"manager":factory.pool[dtoType]=Manager{id:"3"}case"address":factory.pool[dtoType]=Address{id:"4"}}dto=factory.pool[dtoType]}

returndto}

Inthefollowingcode,theDataTransferObjectinterfaceisimplementedbytheCustomerclass:

//DataTransferObjectinterfacetypeDataTransferObjectinterface{getId()string}//CustomerstructtypeCustomerstruct{idstring//sequencegeneratornamestringssnstring}//CustomerclassmethodgetIdfunc(customerCustomer)getId()string{//fmt.Println("gettingcustomerId")returncustomer.id}//EmployeestructtypeEmployeestruct{idstringnamestring}//EmployeeclassmethodgetIdfunc(employeeEmployee)getId()string{returnemployee.id}//ManagerstructtypeManagerstruct{idstringnamestringdeptstring}

TheDataTransferObjectinterfaceisimplementedbythe Managerclass,asshowninthefollowingcode:

//ManagerclassmethodgetIdfunc(managerManager)getId()string{returnmanager.id}//AddressstructtypeAddressstruct{idstringstreetLine1stringstreetLine2stringstatestringcitystring}//AddressclassmethodgetIdfunc(addressAddress)getId()string{returnaddress.id}//mainmethodfuncmain(){varfactory=DataTransferObjectFactory{make(map[string]DataTransferObject)}varcustomerDataTransferObject=factory.getDataTransferObject("customer")fmt.Println("Customer",customer.getId())varemployeeDataTransferObject=factory.getDataTransferObject("employee")fmt.Println("Employee",employee.getId())varmanagerDataTransferObject=factory.getDataTransferObject("manager")fmt.Println("Manager",manager.getId())varaddressDataTransferObject=factory.getDataTransferObject("address")fmt.Println("Address",address.getId())}

Runthefollowingcommands:gorunflyweight.go

Thefollowingscreenshotdisplaystheoutput:

WewilltakealookatPrivateclassandProxydatapatternsinthenextsections.

PrivateclassdataTheprivateclassdatapatternsecuresthedatawithinaclass.Thispatternencapsulatestheinitializationoftheclassdata.Thewriteprivilegesofpropertieswithintheprivateclassareprotected,andpropertiesaresetduringconstruction.Theprivateclasspatternprintstheexposureofinformationbysecuringitinaclassthatretainsthestate.Theencapsulationofclassdatainitializationisascenariowherethispatternisapplicable.Accountisaclasswithaccountdetailsandacustomername.AccountDetailsistheprivateattributeofAccount ,andCustomerNameisthepublicattribute.JSONmarshalingofAccounthas CustomerNameasapublicproperty.AccountDetailsisthepackagepropertyinGo(modeledasprivateclassdata):

//mainpackagehasexamplesshown//inHands-OnDataStructuresandalgorithmswithGobookpackagemain//importingfmtandencoding/jsonpackagesimport("encoding/json""fmt")//AccountDetailsstructtypeAccountDetailsstruct{idstringaccountTypestring}//AccountstructtypeAccountstruct{details*AccountDetailsCustomerNamestring}//AccountclassmethodsetDetailsfunc(account*Account)setDetails(idstring,accountTypestring){account.details=&AccountDetails{id,accountType}}

Asshowninthefollowingcode,theAccountclasshasthe getId method,whichreturnsthe id privateclassattribute:

//AccountclassmethodgetIdfunc(account*Account)getId()string{returnaccount.details.id}//AccountclassmethodgetAccountTypefunc(account*Account)getAccountType()string{returnaccount.details.accountType}

Themainmethodcallsthe AccountinitializerwithCustomerName.Thedetailsoftheaccountaresetdetailswiththe setDetailsmethod:

//mainmethodfuncmain(){varaccount*Account=&Account{CustomerName:"JohnSmith"}account.setDetails("4532","current")jsonAccount,_:=json.Marshal(account)fmt.Println("PrivateClasshidden",string(jsonAccount))fmt.Println("AccountId",account.getId())fmt.Println("AccountType",account.getAccountType())}

Runthefollowingcommands:gorunprivateclass.go

Thefollowingscreenshotdisplaystheoutput:

Let'stakealookatProxypatterninthenextsection.

ProxyTheproxypatternforwardstoarealobjectandactsasaninterfacetoothers.Theproxypatterncontrolsaccesstoanobjectandprovidesadditionalfunctionality.Theadditionalfunctionalitycanberelatedtoauthentication,authorization,andprovidingrightsofaccesstotheresource-sensitiveobject.Therealobjectneednotbemodifiedwhileprovidingadditionallogic.Remote,smart,virtual,andprotectionproxiesarethescenarioswherethispatternisapplied.Itisalsousedtoprovideanalternativetoextendfunctionalitywithinheritanceandobjectcomposition.Aproxyobjectisalsoreferredtoasasurrogate,handle,orwrapper.Theproxypatterncomprisesthe subjectinterface,the RealSubjectclass,andthe Proxyclass:

Subjectisaninterfaceforthe RealObjectandProxyclass.TheRealSubjectobjectiscreatedandmaintainedasareferenceinthe Proxyclass. RealSubjectisresourcesensitive,requiredtobeprotected,andexpensivetocreate.  RealObjectisaclassthatimplementsthe IRealObjectinterface.IthasaperformActionmethod. VirtualProxyisusedtoaccessRealObjectandinvokethe performActionmethod.

Thefollowingcodeshowsanimplementationofproxypattern://mainpackagehasexamplesshown//inHands-OnDataStructuresandalgorithmswithGobookpackagemain//importingfmtpackageimport("fmt")//IRealObjectinterfacetypeIRealObjectinterface{performAction()}//RealObjectstructtypeRealObjectstruct{}RealObjectclassimplementsIRealObjectinterface.TheclasshasmethodperformAction.//RealObjectclassmethodperformActionfunc(realObject*RealObject)performAction(){fmt.Println("RealObjectperformAction()")}//VirtualProxystructtypeVirtualProxystruct{realObject*RealObject}

}

//VirtualProxyclassmethodperformActionfunc(virtualProxy*VirtualProxy)performAction(){ifvirtualProxy.realObject==nil{virtualProxy.realObject=&RealObject{}}fmt.Println("VirtualProxyperformAction()")virtualProxy.realObject.performAction()}//mainmethodfuncmain(){varobjectVirtualProxy=VirtualProxy{}object.performAction()}

Runthefollowingcommands:gorunvirtualproxy.go

Thefollowingscreenshotdisplaystheoutput:

Nowthatweknowtheclassificationofdatastructuresandthedesignpatternsused,let'sgoaheadandtakealookattherepresentationofalgorithms. 

RepresentationofalgorithmsAflowchartandpseudocodearemethodsofrepresentingalgorithms.Analgorithmshowsthelogicofhowaproblemissolved.AflowcharthasdifferentrepresentationsymbolssuchasEntry,Exit,Task,Input/Output,DecisionPoint,andInterBlock.Astructuredprogramconsistsofaseriesofthesesymbolstoperformaspecifictask.Pseudocodehasdocumentation,action,andflowcontrolkeywordstovisualizeanalgorithm.ThedocumentationkeywordsareTASKandREM.SET,PUT,andGETaretheactionkeywords.Let'stakealookatthedifferentrepresentationsofalgorithms,thatis,flowchartsandPseudocodeinthenextsections.

FlowchartTheflowcontrolkeywordsareSET,LOOP,(WHILE,UNTIL),REP,andPOST. Thefollowingflowchartshowsaformulaoranalgorithmtocalculatethedividendgivenanumberofshares,thefacevalue,andthedividendpercentage.ThestartandendaretheEntryandExitsymbols.Theinputnumberofshares,sharefacevalue,anddividendpercentageusetheInputsymbol.ThecomputedividendandoutputdividendusetheTasksymbolandOutputsymbolrespectively:

 Inthenextsection,we'll takealookatpseudocode,representationofalgorithms.

PseudocodePseudocodeisahigh-leveldesignofaprogramoralgorithm.Sequenceandselectionaretwoconstructsusedinpseudocode.Pseudocodeiseasierthanaflowchartvisualizesthealgorithmwhilepseudocodecanbeeasilymodifiedandupdated.Errorsindesigncanbecaughtveryearlyinpseudocode.Thissavesthecostoffixingdefectslater.Togiveanexample,wewanttofindthemaxvalueinanarrayoflengthn.Thepseudocodewillbewrittenasfollows:

maximum(arr){

n<-len(arr)

max<-arr[0]

fork<-0,ndo{

Ifarr[k]>max{

max<-arr[k]

}

}

returnmax

}

Nowthatweknowthedifferentwaystorepresentthealgorithm,let'stakealookathowwecanmonitoritscomplexityandperformanceinthenextsection.

ComplexityandperformanceanalysisTheefficiencyofanalgorithmismeasuredthroughvariousparameters,suchasCPUtime,memory,disk,andnetwork.Thecomplexityishowthealgorithmscaleswhenthenumberofinputparametersincreases.Performanceisameasureoftime,space,memory,andotherparameters.Algorithmsarecomparedbytheirprocessingtimeandresourceconsumption.ComplexitymeasurestheparametersandisrepresentedbytheBigOnotation.

ComplexityanalysisofalgorithmsThecomplexityofanalgorithmismeasuredbythespeedofthealgorithm.Typically,thealgorithmwillperformdifferentlybasedonprocessorspeed,diskspeed,memory,andotherhardwareparameters.Hence,asymptoticalcomplexityisusedtomeasurethecomplexityofanalgorithm.Analgorithmisasetofstepstobeprocessedbydifferentoperationstoachieveatask.Thetimetakenforanalgorithmtocompleteisbasedonthenumberofstepstaken.Let'ssayanalgorithmiteratesthroughanarray, m,ofsize10andupdatetheelementstothesumofindexand200.Thecomputationaltimewillbe10*t,wheret isthetimetakentoadd twointegersandupdatethemtoanarray.Thenextstepwillbeprintingthemafteriteratingoveranarray.The t timeparameterwillvarywiththehardwareofthecomputerused.Asymptotically,thecomputationaltimegrowsasafactorof10,asshowninthefollowingcode:

//mainpackagehasexamplesshown//inHands-OnDataStructuresandalgorithmswithGobookpackagemain//importingfmtpackageimport("fmt")//mainmethodfuncmain(){varm[10]intvarkintfork=0;k<10;k++{m[k]=k+200fmt.Printf("Element[%d]=%d\n",k,m[k])}}

Runthefollowingcommands:goruncomplexity.go

Thefollowingscreenshotdisplaystheoutput:

Let'stakealookatthedifferentcomplexitytypesinthenextsections.

BigOnotation

The T(n)timefunctionrepresentsthealgorithmcomplexitybasedonBigOnotation.T(n)=O(n)statesthatanalgorithmhasalineartimecomplexity.UsingBigOnotation,theconstanttime,lineartime,logarithmictime,cubictime,andquadratictimecomplexityaredifferentcomplexitytypesforanalgorithm.Lineartime, O(n),isusedasameasureofcomplexityinscenariossuchaslinearsearch,traversing,andfindingtheminimumandmaximumnumberofarrayelements.ArrayListandqueuearedatastructuresthathavethesemethods.Analgorithmthathaslogarithmictime, O(logn),isabinarysearchinatreedatastructure.Bubblesort,selectionsort,andinsertionsortalgorithmshavecomplexityofquadratictime, O(n2).BigOmegaΩandbigThetaΘarenotationsforthelowerandupperboundsforaparticularalgorithm.Theworstcase,bestcase,averagecase,andamortizedrun-timecomplexityisusedforanalysisofalgorithms.Amortizedrun-timecomplexityisreferredtoas2n.Asymptotically,itwilltendtoO(1).BigOnotationisalsousedtodeterminehowmuchspaceisconsumedbythealgorithm.Thishelpsusfindthebestandworstcasescenarios,relativetospaceandtime.Let'stakealookatlinearcomplexityinthenextsection.

LinearcomplexityAnalgorithmisoflinearcomplexityiftheprocessingtimeorstoragespaceisdirectlyproportionaltothenumberofinputelementstobeprocessed.InBigOnotation,linearcomplexityispresentedasO(n).StringmatchingalgorithmssuchastheBoyer-MooreandUkkonenhavelinearcomplexity.Linearcomplexity, O(n),isdemonstratedinanalgorithmasfollows:

//mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain//importingfmtpackageimport("fmt")//mainmethodfuncmain(){varm[10]intvarkintfork=0;k<10;k++{m[k]=k*200fmt.Printf("Element[%d]=%d\n",k,m[k])}}

Runthefollowingcommands:gorunlinear_complexity.go

Thefollowingscreenshotdisplaystheoutput:

Let'stakealookatquadraticcomplexityinthenextsection.

QuadraticcomplexityAnalgorithmisofquadraticcomplexityiftheprocessingtimeisproportionaltothesquareofthenumberofinputelements. Inthefollowingcase,thecomplexityofthealgorithmis10*10=100.Thetwoloopshaveamaximumof 10.ThequadraticcomplexityforamultiplicationtableofnelementsisO(n2).Quadraticcomplexity, O(n2),isshowninthefollowingexample:

//mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain//importingfmtpackageimport("fmt")//mainmethodfuncmain(){vark,lintfork=1;k<=10;k++{fmt.Println("MultiplicationTable",k)forl=1;l<=10;l++{varxint=l*kfmt.Println(x)}}}

Runthefollowingcommands:gorunquadratic_complexity.go

Thefollowingscreenshotdisplaystheoutput:

Let'stakealookatcubiccomplexityinthenextsection.

CubiccomplexityInthecaseofcubiccomplexity,theprocessingtimeofanalgorithmisproportionaltothecubeoftheinputelements. Thecomplexityofthefollowingalgorithmis10*10*10=1,000.Thethreeloopshaveamaximumof10.ThecubiccomplexityforamatrixupdateisO(n3).CubiccomplexityO(n3)isexplainedinthefollowingexample:

//mainpackagehasexamplesshown//inHands-OnDataStructuresandalgorithmswithGobookpackagemain//importingfmtpackageimport("fmt")//mainmethodfuncmain(){vark,l,mintvararr[10][10][10]intfork=0;k<10;k++{forl=0;l<10;l++{form=0;m<10;m++{arr[k][l][m]=1fmt.Println("Elementvalue",k,l,m,"is",arr[k][l][m])}}}}

Runthefollowingcommands:goruncubic_complexity.go

Thefollowingscreenshotdisplaystheoutput:

Let'stakealookatlogarithmiccomplexityinthenextsection.

LogarithmiccomplexityAnalgorithmisoflogarithmiccomplexityiftheprocessingtimeisproportionaltothelogarithmoftheinputelements.Thelogarithmbaseistypically2.ThefollowingtreeisabinarytreewithLeftNodeandRightNode.TheinsertoperationisofO(logn)complexity,wherenisthenumberofnodes.Logarithmiccomplexityispresentedasfollows:

//mainpackagehasexamplesshown//inHands-OnDataStructuresandalgorithmswithGobookpackagemain//importingfmtpackageimport("fmt")//TreestructtypeTreestruct{LeftNode*TreeValueintRightNode*Tree}

Asshowninthefollowingcode,theTreeclasshasthe insertmethod,whichinsertstheelementgivenmistheintegerelement:

//Treeinsertmethodforinsertingatmpositionfunc(tree*Tree)insert(mint){iftree!=nil{iftree.LeftNode==nil{tree.LeftNode=&Tree{nil,m,nil}}else{iftree.RightNode==nil{tree.RightNode=&Tree{nil,m,nil}}else{iftree.LeftNode!=nil{tree.LeftNode.insert(m)}else{tree.RightNode.insert(m)}}}}else{tree=&Tree{nil,m,nil}}}//printmethodforprintingaTreefuncprint(tree*Tree){iftree!=nil{fmt.Println("Value",tree.Value)fmt.Printf("TreeNodeLeft")

fmt.Printf("TreeNodeLeft")

print(tree.LeftNode)fmt.Printf("TreeNodeRight")print(tree.RightNode)}else{fmt.Printf("Nil\n")}}

Themainmethodcallstheinsertmethodontreetoinsertthe 1, 3,5,and7 elements,asshowninthefollowingcode:

//mainmethodfuncmain(){vartree*Tree=&Tree{nil,1,nil}print(tree)tree.insert(3)print(tree)tree.insert(5)print(tree)tree.LeftNode.insert(7)print(tree)}

Runthefollowingcommands:goruntree.go

Thefollowingscreenshotdisplaystheoutput:

Nowthatweknowaboutthecomplexitiesinalgorithmsandanalyzingtheirperformance,let'stakealookatbruteforcealgorithmsinthenextsection.

BruteforcealgorithmsAbruteforcealgorithmsolvesaproblembasedonthestatementandtheproblemdefinition.Bruteforcealgorithmsforsearchandsortaresequentialsearchandselectionsort.Exhaustivesearchisanotherbruteforcealgorithmwherethesolutionisinasetofcandidatesolutionswithdefinitiveproperties.Thespaceinwhichthesearchhappensisastateandcombinatorialspace,whichconsistsofpermutations,combinations,orsubsets.BruteForcealgorithmsareknownforwideapplicabilityandsimplicityinsolvingcomplexproblems.Searching,stringmatching,andmatrixmultiplicationaresomescenarioswheretheyareused.Singlecomputationaltaskscanbesolvedusingbruteforcealgorithms.Theydonotprovideefficientalgorithms.Thealgorithmsareslowandnon-performant.Representationofabruteforcealgorithmisshowninthefollowingcode:

//mainpackagehasexamplesshown//inHands-OnDataStructuresandalgorithmswithGobookpackagemain//importingfmtpackageimport("fmt")//findElementmethodgivenarrayandkelementfuncfindElement(arr[10]int,kint)bool{variintfori=0;i<10;i++{ifarr[i]==k{returntrue}}returnfalse}//mainmethodfuncmain(){vararr=[10]int{1,4,7,8,3,9,2,4,1,8}varcheckbool=findElement(arr,10)fmt.Println(check)varcheck2bool=findElement(arr,9)fmt.Println(check2)}

Runthefollowingcommands:gorunbruteforce.go

Thefollowingscreenshotdisplaystheoutput:

Afterbruteforcealgorithms,let'scoverdivideandconqueralgorithmsinthenextsection.

DivideandconqueralgorithmsAdivideandconqueralgorithmbreaksacomplexproblemintosmallerproblemsandsolvesthesesmallerproblems.Thesmallerproblemwillbefurtherbrokendowntillitisaknownproblem.Theapproachistorecursivelysolvethesub-problemsandmergethesolutionsofthesub-problems.Recursion,quicksort,binarysearch,fastFouriertransform,andmergesortaregoodexamplesofdivideandconqueralgorithms.Memoryisefficientlyusedwiththesealgorithms.Performanceissometimesanissueinthecaseofrecursion.Onmultiprocessormachines,thesealgorithmscanbeexecutedondifferentprocessorsafterbreakingthemdownintosub-problems.Adivideandconqueralgorithmisshowninthefollowing code:

//mainpackagehasexamplesshown//inHands-OnDataStructuresandalgorithmswithGobookpackagemain//importingfmtpackageimport("fmt")

Asshowninthefollowingcode,theFibonaccimethodtakesthe k integerparameterandreturnstheFibonaccinumberfork.ThemethodusesrecursiontocalculatetheFibonaccinumbers.Therecursionalgorithmisappliedbydividingtheproblemintothe k-1integerandthe k-2 integer:

//fibonaccimethodgivenkintegerfuncfibonacci(kint)int{ifk<=1{return1}returnfibonacci(k-1)+fibonacci(k-2)}//mainmethodfuncmain(){varmint=5form=0;m<8;m++{varfib=fibonacci(m)fmt.Println(fib)}}

Runthefollowingcommands:gorundivide.go

Thefollowingscreenshotdisplaystheoutput:

Let'stakealookatwhatbacktrackingalgorithmsareinthenextsection.

BacktrackingalgorithmsAbacktrackingalgorithmsolvesaproblembyconstructingthesolutionincrementally.Multipleoptionsareevaluated,andthealgorithmchoosestogotothenextcomponentofthesolutionthroughrecursion.Backtrackingcanbeachronologicaltypeorcantraversethepaths,dependingontheproblemthatyouaresolving.Backtrackingisanalgorithmthatfindscandidatesolutionsandrejectsacandidateonthebasisofitsfeasibilityandvalidity.Backtrackingisusefulinscenariossuchasfindingavalueinanunorderedtable.Itisfasterthanabruteforcealgorithm,whichrejectsalargenumberofsolutionsinaniteration.Constraintsatisfactionproblemssuchasparsing,rulesengine,knapsackproblems,andcombinatorialoptimizationaresolvedusingbacktracking.Thefollowingisanexampleofabacktrackingalgorithm.Theproblemistoidentifythecombinationsofelementsinanarrayof10elementswhosesumisequalto18.ThefindElementsWithSum methodrecursivelytriestofindthecombination.Wheneverthesumgoesbeyondthektarget,itbacktracks:

//mainpackagehasexamplesshown//inHands-OnDataStructuresandalgorithmswithGobookpackagemain//importingfmtpackageimport("fmt")//findElementsWithSumofkfromarrofsizefuncfindElementsWithSum(arr[10]int,combinations[19]int,sizeint,kint,addValueint,lint,mint)int{varnumint=0ifaddValue>k{return-1}ifaddValue==k{num=num+1varpint=0forp=0;p<m;p++{fmt.Printf("%d,",arr[combinations[p]])}fmt.Println("")}variintfori=l;i<size;i++{//fmt.Println("m",m)combinations[m]=lfindElementsWithSum(arr,combinations,size,k,addValue+arr[i],l,m+1)l=l+1

l=l+1

}returnnum}//mainmethodfuncmain(){vararr=[10]int{1,4,7,8,3,9,2,4,1,8}varaddedSumint=18varcombinations[19]intfindElementsWithSum(arr,combinations,10,addedSum,0,0,0)//fmt.Println(check)//varcheck2bool=findElement(arr,9)//fmt.Println(check2)}

Runthefollowingcommands:gorunbacktracking.go

Thefollowingscreenshotdisplaystheoutput:

SummaryThischaptercoveredthedefinitionofabstractdatatypes,classifyingdatastructuresintolinear,nonlinear,homogeneous,heterogeneous,anddynamictypes.Abstractdatatypessuchascontainer,list,set,map,graph,stack,andqueuewerepresentedinthischapter.Thechaptercoveredtheperformanceanalysisofdatastructuresandstructuraldesignpatterns.Welookedattheclassificationofdatastructuresandstructuraldesignpatterns.Youcanusealgorithmssuchasbruteforce,divideandconquer,andbacktrackingbycalculatingthecomplexityandperformanceanalysis.Thechoiceofalgorithmandtheuseofdesignpatternsanddatastructuresarethekeytakeaways. Inthenextchapter,wewilldiscussdatastructuresinGo.Thefollowingdatastructureswillbecovered:

ArraysSlicesTwo-dimensionalslices Maps

Questionsandexercises1. Giveanexamplewhereyoucanuseacompositepattern.2. Foranarrayof10elementswitharandomsetofintegers,identifythemaximumandminimum.Calculatethecomplexityofthealgorithm.

3. Tomanagethestateofanobject,whichstructuralpatternisrelevant?4. Awindowissub-classedtoaddascrollbartomakeitascrollablewindow.Whichpatternisappliedinthisscenario?

5. Findthecomplexityofabinarytreesearchalgorithm.6. Identifythesubmatricesof2x2ina3x3matrix.Whatisthecomplexityofthealgorithmthatyouhaveused?

7. Explainwithascenariothedifferencebetweenbruteforceandbacktrackingalgorithms.1. Arulesengineusesbacktrackingtoidentifytherulesaffectedbythechange.Showanexamplewherebacktrackingidentifiestheaffectedrules.

2. Drawaflowchartforthealgorithmofthecalculationofprofit-lossgiventhecostprice,sellingprice,andquantity.

3. Writethepseudocodeforanalgorithmthatcomparesthestringsandidentifiesthesubstringwithinastring.

Furtherreading

ThefollowingbooksarerecommendedifyouwanttofindoutmoreaboutGangofFourdesignpatterns,algorithms,anddatastructures:

DesignPatterns, byErichGamma,RichardHelm,RalphJohnson,andJohnVlissidesIntroductiontoAlgorithms –ThirdEdition,byThomasH.Cormen,CharlesE.Leiserson,RonaldL.Rivest,andCliffordSteinDatastructuresandAlgorithms:AnEasyIntroduction,by RudolphRussell

GettingStartedwithGoforDataStructuresandAlgorithmsTheGoprogramminglanguagehasbeenrapidlyadoptedbydevelopersforbuildingwebapplications.Withitsimpressiveperformanceandeaseofdevelopment,Goenjoysthesupportofawidevarietyofopensourceframeworksforbuildingscalableandhighlyperformantwebservicesandapps.ThemigrationtoGolanghastakenplacemainlybecauseofitsfast,lightweight,andinbuiltconcurrencyfeatures.Thisbringswithittheneedtolearndatastructuresandalgorithmswiththisgrowinglanguage.Indatastructures,acollectionofelementsofasingletypeiscalledanarray.Slicesaresimilartoarraysexceptthattheyhaveunusualproperties.Sliceoperationssuchasenlargingasliceusingappendandcopymethods,assigningpartsofaslice,appendingaslice,andappendingapartofaslicearepresentedwithcodesamples. DatabaseoperationsandCRUDwebformsarethescenariosinwhichGodatastructuresandalgorithmsaredemonstrated.Inthischapter,wewilldiscussthefollowingGolanguage-specificdatastructures:

ArraysSlicesTwo-dimensionalslicesMapsDatabaseoperationsVariadicfunctionsCRUDwebforms 

TechnicalrequirementsInstallGoVersion1.10at https://golang.org/doc/install,dependingonyouroperatingsystem. ThecodefilesforthischaptercanbefoundatthefollowingGitHubURL: https://github.com/PacktPublishing/Learn-Data-Structures-and-Algorithms-with-Golang/tree/master/Chapter02.Inthischapter,databaseoperationsrequirethe github.com/go-sql-driver/mysql package.Inadditiontothis,MySQL(4.1+)needstobeinstalledfromhttps://dev.mysql.com/downloads/mysql/.Runthefollowingcommand:

goget-ugithub.com/go-sql-driver/mysql

ArraysArraysarethemostfamousdatastructuresindifferentprogramminglanguages.Differentdatatypescanbehandledaselementsinarrayssuchasint,float32,double,andothers.Thefollowingcodesnippetshowstheinitializationofanarray(arrays.go):

vararr=[5]int{1,2,4,5,6}

Anarray'ssizecanbefoundwiththelen()function.Aforloopisusedforaccessingalltheelementsinanarray,asfollows:

variint

fori=0;i<len(arr);i++{

fmt.Println("printingelements",arr[i]

}

Inthefollowingcodesnippet,therangekeywordisexplainedindetail.Therangekeywordcanbeusedtoaccesstheindexandvalueforeachelement:

varvalueint

fori,value=rangearr{

fmt.Println("range",value)

}

The_blankidentifierisusediftheindexisignored.Thefollowing code showshowa _blankidentifiercanbeused:

for_,value=rangearr{

fmt.Println("blankrange",value)

}

Runthefollowingcommand:gorunarrays.go

Thefollowingscreenshotdisplaystheoutput:

Goarraysarenotdynamicbuthaveafixedsize.Toaddmoreelementsthanthesize,abiggerarrayneedstobecreatedandalltheelementsoftheoldoneneedtobecopied.Anarrayispassedasavaluethroughfunctionsbycopyingthearray.Passingabigarraytoafunctionmightbe

functionsbycopyingthearray.Passingabigarraytoafunctionmightbeaperformanceissue.Nowthatwehavecoveredwhatarraysare,let'stakealookatslicesinthenextsection.

SlicesGoSliceisanabstractionoverGoArray. MultipledataelementsofthesametypeareallowedbyGoarrays.ThedefinitionofvariablesthatcanholdseveraldataelementsofthesametypeareallowedbyGoArray,butitdoesnothaveanyprovisionofinbuiltmethodstoincreaseitssizeinGo.ThisshortcomingistakencareofbySlices. AGoslicecanbeappendedtoelementsafterthecapacityhasreacheditssize. Slicesaredynamicandcandoublethe currentcapacity inordertoaddmoreelements.Let'stakealookatthelenfunctioninthenextsection.

Thelenfunction Thelen()functiongivesthecurrentlengthofslice,andthecapacityofslicecanbeobtainedusingthecap()function. Thefollowingcodesampleshowsthebasicslicecreationandappendingaslice(basic_slice.go):

varslice=[]int{1,3,5,6}

slice=append(slice,8)

fmt.Println(“Capacity”,cap(slice))

fmt.Println(“Length”,len(slice))

Runthefollowingcommandtoexecutetheprecedingcode:gorunbasic_slice.go

Thefollowingscreenshotdisplaystheoutput:

Let'stakealookattheslicefunctioninthenextsection.

Slicefunction

Slicesarepassedbyreferringtofunctions.Bigslicescanbepassedtofunctionswithoutimpactingperformance.Passingasliceasareferencetoafunctionisdemonstratedinthecodeasfollows(slices.go):

//twiceValuemethodgivensliceofinttype

functwiceValue(slice[]int){

variint

varvalueint

fori,value=rangeslice{

slice[i]=2*value

}

}

//mainmethod

funcmain(){

varslice=[]int{1,3,5,6}

twiceValue(slice)

variint

fori=0;i<len(slice);i++{

fmt.Println(“newslicevalue”,slice[i])

}

}

Runthefollowingcommand:gorunslices.go

Thefollowingscreenshotdisplaystheoutput:

Nowthatweknowwhatslicesare,let'smoveontotwo-dimensionalslicesinthenextsection.

Two-dimensionalslicesTwo-dimensionalslicesaredescriptorsofatwo-dimensionalarray.Atwo-dimensionalslice isacontiguoussectionofanarraythatisstoredawayfromthesliceitself.Itholdsreferencestoanunderlyingarray.Atwo-dimensionalslicewillbeanarrayofarrays,whilethecapacityofaslicecanbeincreasedbycreatinganewsliceandcopyingthecontentsoftheinitialsliceintothenewone.Thisisalsoreferredtoasasliceofslices.Thefollowingisanexampleofatwo-dimensionalarray.A2Darrayiscreatedandthearrayelementsareinitializedwithvalues.twodarray.goisthecodeexhibitthat'spresentedinthefollowingcode:

//mainpackagehasexamplesshown

//inGoDataStructuresandalgorithmsbook

packagemain

//importingfmtpackage

import(

"fmt"

)

//mainmethod

funcmain(){

varTwoDArray[8][8]int

TwoDArray[3][6]=18

TwoDArray[7][4]=3

TwoDArray[7][4]=3

fmt.Println(TwoDArray)

}

Runthefollowingcommand:goruntwodarray.go

Thefollowingscreenshotdisplaystheoutput:

Fordynamicallocation,weusesliceofslices.Inthefollowingcode,sliceofslicesisexplainedastwo-dimensionalslices—twodslices.go:

//inGoDataStructuresandalgorithmsbook

packagemain

//importingfmtpackage

import(

"fmt"

)

//mainmethod

funcmain(){

varrowsint

varcolsint

rows=7

cols=9

vartwodslices=make([][]int,rows)

variint

fori=rangetwodslices{

twodslices[i]=make([]int,cols)

}

fmt.Println(twodslices)

}

Runthefollowingcommands:

goruntwodslices.go

Thefollowingscreenshotdisplaystheoutput:

 Theappend methodonthesliceisusedtoappendnewelementstotheslice.Iftheslicecapacityhasreachedthesizeoftheunderlyingarray,thenappendincreasesthesizebycreatinganewunderlyingarrayandaddingthenewelement. slic1isasubsliceofarrstartingfromzeroto3(excluded),whileslic2isasubsliceofarrstartingfrom1(inclusive)to5(excluded).Inthefollowingsnippet,theappendmethodcallsonslic2 toaddanew12element(append_slice.go):

vararr=[]int{5,6,7,8,9}

varslic1=arr[:3]

fmt.Println("slice1",slic1)

varslic2=arr[1:5]

fmt.Println("slice2",slic2)

varslic3=append(slic2,12)

fmt.Println("slice3",slic3)

Runthefollowingcommands:gorunappend_slice.go

Thefollowingscreenshotdisplaystheoutput:

Nowthatwehavecoveredwhattwo-dimensionalslicesare,let'stakealookatmapsinthenextsection.

MapsMapsareusedtokeeptrackof keysthataretypes,suchasintegers,strings,float,double,pointers,interfaces,structs,andarrays.Thevaluescanbeofdifferenttypes.Inthefollowingexample,thelanguageofthemaptypewithakeyintegerandavaluestringiscreated(maps.go):

varlanguages=map[int]string{

3:“English”,

4:“French”,

5:“Spanish”

}

Mapscanbecreatedusingthemake method,specifyingthekeytypeandthevaluetype.Productsofa maptypewithakeyintegerandvaluestringareshowninthefollowingcodesnippet:

varproducts=make(map[int]string)

products[1]=“chair”

products[2]=“table”

Aforloopisusedforiteratingthroughthemap.Thelanguagesmapisiteratedasfollows:

variint

varvaluestring

fori,value=rangelanguages{

fmt.Println("language",i,“:",value)

}

fmt.Println("productwithkey2",products[2])

Retrievingvalueanddeleting slice operationsusingtheproductsmap isshowninthefollowingcode:

fmt.Println(products[2])

delete(products,”chair”)

fmt.Println("products",products)

Runthefollowingcommands:gorunmaps.go

Thefollowingscreenshotdisplaystheoutput:

Nowthatwe'vecoveredmaps,let'smoveontodatabaseoperations.

DatabaseoperationsInthissection,wewilltakealookatsomeofdatabaseoperationsusingappropriateexamples. Let'sstartwiththeGetCustomermethodinthenextsection. 

TheGetCustomermethod

TheGetCustomermethodretrievestheCustomerdatafromthedatabase.Tostartwith,thecreate databaseoperationisshowninthefollowingexample.Customeristhetablewiththe Customerid,CustomerName,andSSNattributes.The GetConnectionmethodreturnsthedatabaseconnection,whichisusedtoquerythedatabase.Thequerythenreturnstherowsfromthedatabasetable.Inthefollowingcode,databaseoperationsareexplainedindetail(database_operations.go):

//mainpackagehasexamplesshown//inHands-OnDataStructuresandalgorithmswithGobookpackagemain

//importingfmt,database/sql,net/http,text/templatepackageimport("fmt""database/sql"_"github.com/go-sql-driver/mysql")

//CustomerClasstypeCustomerstruct{CustomerIdintCustomerNamestringSSNstring}//GetConnectionmethodwhichreturnssql.DBfuncGetConnection()(database*sql.DB){databaseDriver:="mysql"databaseUser:="newuser"databasePass:="newuser"databaseName:="crm"database,error:=sql.Open(databaseDriver,databaseUser+":"+databasePass+"@/"+databaseName)iferror!=nil{panic(error.Error())}returndatabase}//GetCustomersmethodreturnsCustomerArrayfuncGetCustomers()[]Customer{vardatabase*sql.DBdatabase=GetConnection()

varerrorerrorvarrows*sql.Rowsrows,error=database.Query("SELECT*FROMCustomerORDERBYCustomeridDESC")iferror!=nil{

iferror!=nil{

panic(error.Error())}varcustomerCustomercustomer=Customer{}

varcustomers[]Customercustomers=[]Customer{}forrows.Next(){varcustomerIdintvarcustomerNamestringvarssnstringerror=rows.Scan(&customerId,&customerName,&ssn)iferror!=nil{panic(error.Error())}customer.CustomerId=customerIdcustomer.CustomerName=customerNamecustomer.SSN=ssncustomers=append(customers,customer)}

deferdatabase.Close()

returncustomers}

//mainmethodfuncmain(){

varcustomers[]Customercustomers=GetCustomers()fmt.Println("Customers",customers)

}

Runthefollowingcommands:gorundatabase_operations.go

Thefollowingscreenshotdisplaystheoutput:

Let'stakealookattheInsertCustomermethodinthenextsection.

TheInsertCustomermethod

TheINSERToperationisasfollows.TheInsertCustomermethodtakestheCustomerparameter andcreatesapreparedstatementfortheINSERTstatement.Thestatementisusedtoexecutetheinsertionofcustomerrowsintothetable,asshowninthefollowingsnippet:

//InsertCustomermethodwithparametercustomerfuncInsertCustomer(customerCustomer){vardatabase*sql.DBdatabase=GetConnection()

varerrorerrorvarinsert*sql.Stmtinsert,error=database.Prepare("INSERTINTOCUSTOMER(CustomerName,SSN)VALUES(?,?)")iferror!=nil{panic(error.Error())}insert.Exec(customer.CustomerName,customer.SSN)

deferdatabase.Close()

}

Let'stakealookatthevariadicfunctionsinthenextsection.

VariadicfunctionsAfunctioninwhichwepassaninfinitenumberofarguments,insteadofpassingthemoneatatime,iscalledavariadicfunction. Thetypeofthefinalparameterisprecededbyanellipsis(...),whiledeclaringavariadicfunction;thisshowsusthatthefunctionmightbecalledwithanynumberofargumentsofthistype.Variadicfunctionscanbeinvokedwithavariablenumberofparameters.fmt.Printlnisacommonvariadicfunction,asfollows:

//mainmethodfuncmain(){

varcustomers[]Customer

customers=GetCustomers()

fmt.Println("BeforeInsert",customers)

varcustomerCustomer

customer.CustomerName="ArnieSmith"

customer.SSN="2386343"

InsertCustomer(customer)

customers=GetCustomers()

fmt.Println("AfterInsert",customers)}

Runthefollowingcommands:gorundatabase_operations.go

Thefollowingscreenshotdisplaystheoutput:

Let'sstarttheupdateoperationinthenextsection.

Theupdateoperation

Theupdate operationisasfollows.The UpdateCustomermethodtakestheCustomerparameter andcreatesapreparedstatementfortheUPDATEstatement.Thestatementisusedtoupdateacustomerrowinthetable:

//UpdateCustomermethodwithparametercustomerfuncUpdateCustomer(customerCustomer){

vardatabase*sql.DB

database=GetConnection()

varerrorerror

varupdate*sql.Stmt

update,error=database.Prepare("UPDATECUSTOMERSETCustomerName=?,SSN=?WHERECustomerId=?")

iferror!=nil{

panic(error.Error())

}update.Exec(customer.CustomerName,customer.SSN,customer.CustomerId)

deferdatabase.Close()

}//mainmethod

funcmain(){

funcmain(){

varcustomers[]Customer

customers=GetCustomers()

fmt.Println("BeforeUpdate",customers)

varcustomerCustomer

customer.CustomerName="GeorgeThompson"

customer.SSN="23233432"

customer.CustomerId=5

UpdateCustomer(customer)

customers=GetCustomers()

fmt.Println("AfterUpdate",customers)}

Runthefollowingcommands:gorundatabase_operations.go

Thefollowingscreenshotdisplaystheoutput:

Let'stakealookatthedeleteoperationinthenextsection.

Thedeleteoperation

Thedeleteoperationisasfollows.TheDeleteCustomermethodtakestheCustomerparameterandcreatesapreparedstatementfortheDELETEstatement.Thestatementisusedtoexecutethedeletionofacustomerrowinthetable:

//DeleteCustomermethodwithparametercustomerfuncdeleteCustomer(customerCustomer){

vardatabase*sql.DB

database=GetConnection()

varerrorerror

vardelete*sql.Stmt

delete,error=database.Prepare("DELETEFROMCustomerWHERECustomerid=?")

iferror!=nil{

panic(error.Error())

}

delete.Exec(customer.CustomerId)

deferdatabase.Close()

}//mainmethod

funcmain(){

varcustomers[]Customer

customers=GetCustomers()

fmt.Println("BeforeDelete",customers)

varcustomerCustomer

customer.CustomerName="GeorgeThompson"

customer.SSN="23233432"

customer.CustomerId=5

deleteCustomer(customer)

customers=GetCustomers()

fmt.Println("AfterDelete",customers)

}

Runthefollowingcommands:

gorundatabase_operations.go

Thefollowingscreenshotdisplaystheoutput:

Nowthatwearedonewithvariadicfunctions,let'sgoaheadandlookatCRUDwebformsinthenextsection.

CRUDwebformsInthissection,wewillexplainwebforms usingbasicexamples,showingyouhowtoperformvariousactions.TostartabasicHTMLpagewiththeGonet/httppackage,thewebformsexampleisasfollows(webforms.go).Thishasawelcomegreetinginmain.html:

//mainpackagehasexamplesshown

//inHands-OnDataStructuresandalgorithmswithGobook

packagemain

//importingfmt,database/sql,net/http,text/templatepackage

import(

"net/http"

"text/template"

"log")

//Homemethodrendersthemain.html

funcHome(writerhttp.ResponseWriter,reader*http.Request){

vartemplate_html*template.Template

template_html=template.Must(template.ParseFiles("main.html"))

template_html.Execute(writer,nil)

template_html.Execute(writer,nil)

}

//mainmethod

funcmain(){

log.Println("Serverstartedon:http://localhost:8000")

http.HandleFunc("/",Home)

http.ListenAndServe(":8000",nil)

}

Thecodeformain.htmlisasfollows:<html>

<body>

<p>WelcometoWebForms</p>

</body>

</html>

Runthefollowingcommands:gorunwebforms.go

Thefollowingscreenshotdisplaystheoutput:

Thewebbrowseroutputisshowninthefollowingscreenshot:

TheCRMapplicationisbuiltwithwebformsasanexampletodemonstrateCRUDoperations.Wecanusethedatabaseoperationswebuiltintheprevioussection.Inthefollowingcode,the crmdatabaseoperationsarepresented.ThecrmdatabaseoperationsconsistofCRUDmethodssuchasCREATE,READ,UPDATE,andDELETEcustomeroperations.The GetConnectionmethodretrievesthedatabaseconnectionforperformingthedatabaseoperations(crm_database_operations.go):

//mainpackagehasexamplesshown

//inHands-OnDataStructuresandalgorithmswithGobook

packagemain

//importingfmt,database/sql,net/http,text/templatepackage

import(

"database/sql"

_"github.com/go-sql-driver/mysql"

)//CustomerClass

typeCustomerstruct{

CustomerIdint

CustomerNamestring

SSNstring

}//GetConnectionmethodwhichreturnssql.DB

funcGetConnection()(database*sql.DB){

databaseDriver:="mysql"

databaseUser:="newuser"

databasePass:="newuser"

databaseName:=“crm"

database,error:=sql.Open(databaseDriver,

database,error:=sql.Open(databaseDriver,

databaseUser+”:"+databasePass+"@/"+databaseName)

iferror!=nil{

panic(error.Error())

}

returndatabase

}

Asshowninthefollowingcode,theGetCustomerByIdmethodtakesthe customerIdparametertolookupinthecustomerdatabase.TheGetCustomerByIdmethodreturnsthecustomerobject:

//GetCustomerByIdwithparametercustomerIdreturnsCustomer

funcGetCustomerById(customerIdint)Customer{

vardatabase*sql.DB

database=GetConnection()

varerrorerror

varrows*sql.Rows

rows,error=database.Query("SELECT*FROMCustomerWHERECustomerId=?",customerId)

iferror!=nil{

panic(error.Error())

}

varcustomerCustomer

customer=Customer{}

forrows.Next(){

varcustomerIdint

varcustomerNamestring

varSSNstring

error=rows.Scan(&customerId,&customerName,&SSN)

iferror!=nil{

panic(error.Error())

}

customer.CustomerId=customerId

customer.CustomerName=customerName

customer.SSN=SSN

}

NowthatwehavecoveredCRUDwebforms,let'smoveontodeferandpanicinthenextsection.

ThedeferandpanicstatementsThedeferstatementdefersthe executionofthefunctionuntilthesurroundingfunctionreturns.Thepanicfunctionstopsthecurrentflowandcontrol.Deferredfunctionsareexecutednormallyafterthepaniccall. Inthefollowingcodeexample,thedefercallgetsexecutedevenwhenthepaniccallisinvoked:

deferdatabase.Close()

returncustomer

}//GetCustomersmethodreturnsCustomerArray

funcGetCustomers()[]Customer{

vardatabase*sql.DB

database=GetConnection()

varerrorerror

varrows*sql.Rows

rows,error=database.Query("SELECT*FROMCustomerORDERBYCustomeridDESC")

iferror!=nil{

panic(error.Error())

}

varcustomerCustomer

customer=Customer{}

varcustomers[]Customer

customers=[]Customer{}

forrows.Next(){

varcustomerIdint

varcustomerNamestring

varssnstring

error=rows.Scan(&customerId,&customerName,&ssn)

iferror!=nil{

panic(error.Error())

}

customer.CustomerId=customerId

customer.CustomerName=customerName

customer.SSN=ssn

customers=append(customers,customer)

}

deferdatabase.Close()

returncustomers

}

Let'stakealookattheInsertCustomer,UpdateCustomer,andDeleteCustomermethodsinthefollowingsections.

TheInsertCustomermethod

Inthefollowingcode,the InsertCustomermethodtakescustomerasaparametertoexecutetheSQLstatementforinsertingintotheCUSTOMERtable:

//InsertCustomermethodwithparametercustomerfuncInsertCustomer(customerCustomer){vardatabase*sql.DBdatabase=GetConnection()varerrorerrorvarinsert*sql.Stmtinsert,error=database.Prepare("INSERTINTOCUSTOMER(CustomerName,SSN)VALUES(?,?)")iferror!=nil{panic(error.Error())}insert.Exec(customer.CustomerName,customer.SSN)deferdatabase.Close()}

TheUpdateCustomermethod

TheUpdateCustomermethodpreparestheUPDATEstatementbypassingtheCustomerNameandSSNfromthe customerobject;thisisshowninthefollowingcode:

//UpdateCustomermethodwithparametercustomerfuncUpdateCustomer(customerCustomer){vardatabase*sql.DBdatabase=GetConnection()varerrorerrorvarupdate*sql.Stmtupdate,error=database.Prepare("UPDATECUSTOMERSETCustomerName=?,SSN=?WHERECustomerId=?")iferror!=nil{panic(error.Error())}update.Exec(customer.CustomerName,customer.SSN,customer.CustomerId)deferdatabase.Close()}

TheDeleteCustomermethod

TheDeleteCustomermethoddeletesthecustomerthat's passedbyexecutingtheDELETEstatement:

//DeleteCustomermethodwithparametercustomerfuncDeleteCustomer(customerCustomer){vardatabase*sql.DBdatabase=GetConnection()varerrorerrorvardelete*sql.Stmtdelete,error=database.Prepare("DELETEFROMCustomerWHERECustomerid=?")iferror!=nil{panic(error.Error())}delete.Exec(customer.CustomerId)deferdatabase.Close()}

Let'stakealookattheCRMwebapplicationinthenextsection.

CRMwebapplication

TheCRMwebapplicationisshownasfollows,withvariouswebpathshandled.TheCRMapplicationcodeisshowninthefollowingcode.The HomefunctionexecutestheHometemplatewiththewriterparameter andthecustomersarray(crm_app.go):

//mainpackagehasexamplesshown//inHands-OnDataStructuresandalgorithmswithGobookpackagemain

//importingfmt,database/sql,net/http,text/templatepackageimport("fmt""net/http""text/template""log")

vartemplate_html=template.Must(template.ParseGlob("templates/*"))

//Home-executeTemplatefuncHome(writerhttp.ResponseWriter,request*http.Request){varcustomers[]Customercustomers=GetCustomers()log.Println(customers)template_html.ExecuteTemplate(writer,"Home",customers)

}

Let'stakealookattheCreate,Insert,Alter,Update,and Deletefunctions,aswellasthemainmethodinthefollowingsections.

TheCreatefunction

Asshowninthefollowingcode,theCreatefunctiontakesthe writerandrequestparameterstorenderthe Create template:

//Create-executeTemplatefuncCreate(writerhttp.ResponseWriter,request*http.Request){

template_html.ExecuteTemplate(writer,"Create",nil)}

TheInsertfunction

TheInsertfunctioninvokestheGetCustomersmethodtogetanarrayofcustomersandrenders the Hometemplatewiththe writerandcustomersarraysasparametersbyinvokingthe ExecuteTemplatemethod.Thisisshowninthefollowingcode:

//Insert-executetemplatefuncInsert(writerhttp.ResponseWriter,request*http.Request){

varcustomerCustomercustomer.CustomerName=request.FormValue("customername")customer.SSN=request.FormValue("ssn")InsertCustomer(customer)varcustomers[]Customercustomers=GetCustomers()template_html.ExecuteTemplate(writer,"Home",customers)

}

TheAlterfunction

ThefollowingcodeshowshowtheAlterfunctionrenderstheHometemplatebyinvokingthe ExecuteTemplatemethodwiththe writerandcustomersarraysasparameters:

//Alter-executetemplatefuncAlter(writerhttp.ResponseWriter,request*http.Request){

varcustomerCustomervarcustomerIdintvarcustomerIdStrstringcustomerIdStr=request.FormValue("id")fmt.Sscanf(customerIdStr,"%d",&customerId)customer.CustomerId=customerIdcustomer.CustomerName=request.FormValue("customername")customer.SSN=request.FormValue("ssn")UpdateCustomer(customer)varcustomers[]Customercustomers=GetCustomers()template_html.ExecuteTemplate(writer,"Home",customers)

}

TheUpdatefunction

TheUpdatefunctioninvokestheExecuteTemplatemethodwithwriterandcustomerlookedupbyid.TheExecuteTemplatemethodrendersthe UPDATE template:

//Update-executetemplatefuncUpdate(writerhttp.ResponseWriter,request*http.Request){

varcustomerIdintvarcustomerIdStrstringcustomerIdStr=request.FormValue("id")fmt.Sscanf(customerIdStr,"%d",&customerId)varcustomerCustomercustomer=GetCustomerById(customerId)

template_html.ExecuteTemplate(writer,"Update",customer)

}

TheDeletefunction

TheDeletemethodrenderstheHometemplateafterdeletingthecustomerthat'sfoundbythe GetCustomerByIdmethod.TheViewmethodrenderstheViewtemplateafterfindingthecustomerbyinvokingthe GetCustomerByIdmethod:

//Delete-executeTemplatefuncDelete(writerhttp.ResponseWriter,request*http.Request){varcustomerIdintvarcustomerIdStrstringcustomerIdStr=request.FormValue("id")fmt.Sscanf(customerIdStr,"%d",&customerId)varcustomerCustomercustomer=GetCustomerById(customerId)DeleteCustomer(customer)varcustomers[]Customercustomers=GetCustomers()template_html.ExecuteTemplate(writer,"Home",customers)

}//View-executeTemplatefuncView(writerhttp.ResponseWriter,request*http.Request){varcustomerIdintvarcustomerIdStrstringcustomerIdStr=request.FormValue("id")fmt.Sscanf(customerIdStr,"%d",&customerId)varcustomerCustomercustomer=GetCustomerById(customerId)fmt.Println(customer)varcustomers[]Customercustomers=[]Customer{customer}customers.append(customer)template_html.ExecuteTemplate(writer,"View",customers)

}

Themainmethod

Themainmethodhandlesthe Home,Alter,Create, Update,View,Insert,andDeletefunctionswithdifferentaliasesforlookupandrendersthetemplatesappropriately.HttpServerlistenstoport8000andwaitsfortemplatealiasinvocation:

//mainmethodfuncmain(){log.Println("Serverstartedon:http://localhost:8000")http.HandleFunc("/",Home)http.HandleFunc("/alter",Alter)http.HandleFunc("/create",Create)http.HandleFunc("/update",Update)http.HandleFunc("/view",View)http.HandleFunc("/insert",Insert)http.HandleFunc("/delete",Delete)http.ListenAndServe(":8000",nil)}

Let'stakealookattheHeader,Footer,Menu,Create,Update,andViewtemplatesinthefollowingsections.

TheHeadertemplateTheHeadertemplatehastheHTMLheadandbody definedinthecodesnippet,asfollows.TheTITLE tagofthewebpageissettoCRMandthewebpagehasCustomerManagement–CRMascontent(Header.tmpl):

{{define"Header"}}

<!DOCTYPEhtml>

<html>

<head>

<title>CRM</title>

<metacharset="UTF-8"/>

</head>

<body>

<h1>CustomerManagement–CRM</h1>

{{end}}

TheFootertemplateTheFootertemplatehastheHTMLandBODYclosetagsdefined.The Footertemplateispresentedinthefollowingcodesnippet(Footer.tmpl):

{{define"Footer"}}

</body>

</html>

{{end}}

TheMenutemplateTheMenutemplatehasthelinksdefinedforHomeandCreateCustomer,asshowninthefollowingcode(Menu.tmpl):

{{define"Menu"}}

<ahref="/">Home</a>|<ahref="/create">CreateCustomer</a>

{{end}}

TheCreatetemplateTheCreatetemplateconsistsofHeader,Menu,andFootertemplates.Theformtocreatecustomerfieldsisfoundinthecreatetemplate.Thisformissubmittedtoawebpath—/insert,asshowninthefollowingcodesnippet(Create.tmpl):

{{define"Create"}}

{{template"Header"}}

{{template"Menu"}}

<br>

<h1>CreateCustomer</h1>

<br>

<br>

<formmethod="post"action="/insert">

CustomerName:<inputtype="text"name="customername"placeholder="customername"autofocus/>

<br>

<br>

SSN:<inputtype="text"name="ssn"placeholder="ssn"/>

SSN:<inputtype="text"name="ssn"placeholder="ssn"/>

<br>

<br>

<inputtype="submit"value="CreateCustomer"/>

</form>

{{template"Footer"}}

{{end}}

TheUpdatetemplateTheUpdatetemplateconsistsofthe Header,Menu,andFootertemplates,asfollows.TheformtoupdatecustomerfieldsisfoundintheUpdatetemplate.Thisformissubmittedtoawebpath, /alter (Update.tmpl):

{{define"Update"}}{{template"Header"}}{{template"Menu"}}<br><h1>UpdateCustomer</h1><br><br><formmethod="post"action="/alter"><inputtype="hidden"name="id"value="{{.CustomerId}}"/>CustomerName:<inputtype="text"name="customername"placeholder="customername"value="{{.CustomerName}}"autofocus><br><br>SSN:<inputtype="text"name="ssn"value="{{.SSN}}"placeholder="ssn"/><br><br><inputtype="submit"value="UpdateCustomer"/></form>{{template"Footer"}}{{end}}

TheViewtemplateTheViewtemplateconsistsofHeader,Menu,andFootertemplates.TheformtoviewthecustomerfieldsisfoundintheViewtemplate,whichispresentedincode asfollows(View.tmpl):

{{define"View"}}

{{template"Header"}}

{{template"Menu"}}

<br>

<h1>ViewCustomer</h1>

<br>

<br>

<tableborder="1">

<tr>

<td>CustomerId</td>

<td>CustomerName</td>

<td>SSN</td>

<td>Update</td>

<td>Delete</td>

<td>Delete</td>

</tr>

{{if.}}

{{range.}}

<tr>

<td>{{.CustomerId}}</td>

<td>{{.CustomerName}}</td>

<td>{{.SSN}}</td>

<td><ahref="/delete?id={{.CustomerId}}"onclick="returnconfirm('Areyousureyouwanttodelete?');">Delete</a></td>

<td><ahref="/update?id={{.CustomerId}}">Update</a></td>

</tr>

{{end}}

{{end}}

</table>

{{template"Footer"}}

{{end}}

Runthefollowingcommands:

goruncrm_app.gocrm_database_operations.go

Thefollowingscreenshotdisplaystheoutput:

Thewebbrowseroutputisshowninthefollowingscreenshot:

SummaryThischapterintroduceddatabaseoperationsandwebforms.Now,youwillbeabletobuildwebapplicationsthatcanstoredataindatabases.Arrays,slices,two-dimensionalslices,andmapswerecoveredwithcodesamples.Arraymethodssuchaslen,iteratingthroughanarrayusingfor,andrangewereexplainedinthischapterusingcodesnippets.Two-dimensionalarraysandsliceofsliceswerediscussedintheSlicessection.Mapswereexplainedwithvariousscenariossuchasaddingkeysandvalues,aswellasretrievinganddeletingvalues.Mapsofdifferenttypes,suchasstringsandintegers,werealsodiscussedinthischapter.Furthermore,variadicfunctions,deferredfunctioncalls,andpanicandrecoveroperationsweredemonstratedintheDatabaseoperationsandCRUDwebforms sections.TheCRMapplicationwasbuiltasawebapplicationwithdatapersistedintheMySQLdatabase. Databaseoperationsforadding,deleting,updating,andretrievingdatawereshownincodesnippets.Inaddition,webformsforcreating,updating,deleting,andviewingcustomerdatawerepresentedusingwebformswithtemplates.MySQLdriveranditsinstallationdetailswereprovidedintheTechnicalrequirementssectionofthischapter.Howtocreatea webapplicationusingGowasdemonstratedwithexecutiondetails.Thenextchapterwillhavetopicsrelatedto lineardatastructuressuchaslists,sets,tuples,andstacks.

Questions1. Whatisthenameofthemethodtogetthesizeofanarray?2. Howdoyoufindthecapacityoftheslice?3. Howdoyouinitializethe2Dsliceofastringtype?4. Howdoyouaddanelementtotheslice?5. Usingcode,canyoudemonstratehowtocreateamapofkeystringsandvaluestrings?Initializethemapwithkeysandvaluesinthecode,iteratetheminaloop,andprintthekeysandvaluesinthecode.1.  Howdoyoudeleteavalueinamap?2. Whatparametersarerequiredforgettingadatabaseconnection?3. Whichsql.Rowsclassmethodmakesitpossibletoreadtheattributesoftheentityinatable?

4. Whatdoesdeferdowhenadatabaseconnectionisclosed?5. Whichmethodallowsthesql.DBclasstocreateapreparedstatement?

Furtherreading

Toreadmoreaboutarrays,mapsandslices,thefollowinglinksarerecommended:

LearningGoDataStructuresandAlgorithms[Video],by GustavoChaínMasteringGo,by MihalisTsoukalos

Section2:BasicDataStructuresandAlgorithmsusingGo

Wewilltalkaboutdatastructures,includinglinear,non-linear,homogeneous,heterogeneous,anddynamictypes,aswellas classicalgorithms.Thissectioncoversdifferenttypesoflists,trees,arrays,sets,dictionaries,tuples,heaps,queues,andstacks,alongwithsorting,recursion,searching,andhashingalgorithms.Thissectioncontainsthefollowingchapters:

Chapter3, LinearDataStructuresChapter4, Non-LinearDataStructuresChapter5, HomogeneousDataStructuresChapter6, HeterogeneousDataStructuresChapter7, DynamicDataStructuresChapter8, ClassicAlgorithms

LinearDataStructuresVariousapplications,suchasFacebook,Twitter,andGoogle,uselistsandlineardatastructures.Aswehavediscussedpreviously,datastructuresallowustoorganizevastswathesofdatainasequentialandorganizedmanner,therebyreducingtimeandeffortinworkingwithsuchdata.Lists,stacks,sets,andtuplesaresomeofthecommonlyusedlineardatastructures.Inthischapter, wewilldiscussthesedatastructuresbygivingexamplesofvariousproceduresinvolvingthem.Wewilldiscussthevariousoperationsrelatedtothesedatastructures,suchasinsertion,deletion,updating,traversing(oflists),reversing,andmergingwithvariouscodesamples. Wewillcoverthefollowinglineardatastructuresinthischapter:

ListsSetsTuplesStacks

TechnicalrequirementsInstallGoversion1.10athttps://golang.org/doc/install,dependingonyouroperatingsystem.ThecodefilesforthischaptercanbefoundatthefollowingGitHubURL: https://github.com/PacktPublishing/Learn-Data-Structures-and-Algorithms-with-Golang/tree/master/Chapter03.

ListsAlistisacollectionoforderedelements thatareusedtostorelistofitems. Unlikearraylists,thesecanexpandandshrinkdynamically.Listsalsobeusedasabaseforotherdatastructures,suchasstackandqueue.Listscanbeusedtostorelistsofusers,carparts,ingredients,to-doitems,andvariousothersuchelements.Listsarethemostcommonlyusedlineardatastructures. Thesewereintroducedinthelispprogramminglanguage.Inthischapter,linkedlistanddoublylinkedlistarethelistswewillcoverintheGolanguage.Let'sdiscusstheoperationsrelatedtoadd,update,remove,andlookuponlinkedlistanddoublylinkedlistinthefollowingsection.

LinkedListLinkedListisasequenceofnodesthathavepropertiesandareferencetothenextnodeinthesequence.Itisalineardatastructurethatisusedtostoredata.Thedatastructurepermitstheadditionanddeletionofcomponentsfromanynodenexttoanothernode.Theyarenot storedcontiguouslyinmemory,whichmakesthemdifferentarrays.Thefollowingsectionswilllookatthestructuresandmethodsinalinkedlist.

TheNodeclassTheNodeclasshasanintegertypedvariablewiththenameproperty.TheclasshasanothervariablewiththenamenextNode,whichisanodepointer.Linkedlistwillhaveasetofnodeswithintegerproperties, asfollows:

//NodeclasstypeNodestruct{propertyintnextNode*Node}

TheLinkedListclassTheLinkedListclasshastheheadNodepointerasitsproperty.Bytraversingto nextNodefromheadNode,youcaniteratethroughthelinkedlist,asshowninthefollowingcode:

//LinkedListclasstypeLinkedListstruct{headNode*Node}

ThedifferentmethodsoftheLinkedListclass,suchasAddtoHead,IterateList,LastNode,AddtoEnd,NodeWithValue,AddAfter,andthemainmethod,arediscussedinthefollowingsections.

TheAddToHeadmethod

TheAddToHeadmethodaddsthenodetothestartofthelinkedlist.TheAddToHeadmethod ofthe LinkedListclasshasaparameterintegerproperty.Thepropertyisusedtoinitializethenode.Anewnodeisinstantiatedanditspropertyissettothe property parameterthat'spassed. ThenextNodepointstothecurrentheadNodeoflinkedList,and headNodeissettothepointerofthenewnodethat'screated,asshowninthefollowingcode:

//AddToHeadmethodofLinkedListclassfunc(linkedList*LinkedList)AddToHead(propertyint){varnode=Node{}node.property=propertyifnode.nextNode!=nil{node.nextNode=linkedList.headNode}linkedList.headNode=&node}

Whenthenodewiththe 1 propertyisaddedtothehead,addingthe1 propertytotheheadoflinkedListsets headNodetocurrentNodewithavalueof 1,asyoucanseeinthefollowingscreenshot:

Let'sexecutethiscommandusingthemainmethod.Here, wehavecreatedaninstanceofaLinkedList classandaddedthe 1 and 3 integerpropertiestotheheadofthisinstance.Thelinkedlist'sheadNodepropertyisprintedafteraddingtheelements,asfollows:

//mainmethodfuncmain(){varlinkedListLinkedListlinkedList=LinkedList{}linkedList.AddToHead(1)linkedList.AddToHead(3)fmt.Println(linkedList.headNode.property)}

Runthefollowingcommandstoexecutethe linked_list.gofile:gorunlinked_list.go

Afterexecutingtheprecedingcommand,wegetthefollowingoutput:

Let'stakealookattheIterateListmethodinthenextsection.

TheIterateListmethod

TheIterateListmethodoftheLinkedListclassiteratesfromtheheadNode propertyandprintsthepropertyofthecurrentheadnode.Theiterationhappenswiththeheadnodemovesto nextNodeoftheheadNode propertyuntilthecurrentnodeisnolongerequaltonil.ThefollowingcodeshowstheIterateListmethodofthe LinkedListclass:

//IterateListmethoditeratesoverLinkedListfunc(linkedList*LinkedList)IterateList(){varnode*Nodefornode=linkedList.headNode;node!=nil;node=node.nextNode{fmt.Println(node.property)}}

TheLastNodemethod

TheLastNodemethodofLinkedListreturnsthenodeattheendofthelist.Thelististraversedtocheckwhether nextNodeisnilfrom nextNode of headNode,asfollows:

//LastNodemethodreturnsthelastNode

func(linkedList*LinkedList)LastNode()*Node{varnode*NodevarlastNode*Nodefornode=linkedList.headNode;node!=nil;node=node.nextNode{ifnode.nextNode==nil{lastNode=node}}returnlastNode}

TheAddToEndmethod

TheAddToEndmethodaddsthenodeattheendofthelist.Inthefollowingcode,thecurrent lastNodeisfoundanditsnextNode propertyissetastheaddednode:

//AddToEndmethodaddsthenodewithpropertytotheend

func(linkedList*LinkedList)AddToEnd(propertyint){varnode=&Node{}node.property=propertynode.nextNode=nilvarlastNode*NodelastNode=linkedList.LastNode()iflastNode!=nil{lastNode.nextNode=node}}

Inthefollowingscreenshot,the AddToEnd methodisinvokedwhenthenodewithapropertyvalue of 5isaddedtotheend.Addingthepropertythroughthismethodcreatesanodewithavalueof 5.Thelastnodeofthelisthasapropertyvalueof 5.ThenextNode propertyof lastNodeisnil.ThenextNodeof lastNodeissettothenodewithavalueof 5:

Let'stakealookattheNodeWithValuemethodinthenextsection.

TheNodeWithValuemethod

Inthefollowingcodesnippet,the NodeWithValuemethodofLinkedListreturnsthenodewiththeproperty value. Thelististraversedandcheckedtoseewhetherthepropertyvalueisequaltotheparameterproperty:

//NodeWithValuemethodreturnsNodegivenparameterproperty

func(linkedList*LinkedList)NodeWithValue(propertyint)*Node{varnode*NodevarnodeWith*Nodefornode=linkedList.headNode;node!=nil;node=node.nextNode{ifnode.property==property{nodeWith=nodebreak;}}returnnodeWith}

TheAddAftermethod

TheAddAftermethodaddsthenodeafteraspecificnode.TheAddAftermethodofLinkedListhas nodePropertyandpropertyparameters.Anodewiththe nodeProperty valueisretrievedusingthe NodeWithValuemethod.Anodewithpropertyiscreatedandaddedafterthe NodeWithnode,asfollows:

//AddAftermethodaddsanodewithnodePropertyafternodewithproperty

func(linkedList*LinkedList)AddAfter(nodePropertyint,propertyint){varnode=&Node{}node.property=propertynode.nextNode=nilvarnodeWith*NodenodeWith=linkedList.NodeWithValue(nodeProperty)ifnodeWith!=nil{node.nextNode=nodeWith.nextNodenodeWith.nextNode=node}}

Youthengetthefollowingoutputwhenthe AddAfter methodisinvokedwhenthenodewitha propertyvalueof 7isaddedafterthenodewithavalueof 1. ThenextNode propertyofthenodewithapropertyvalue of 1isnil.ThenextNode propertyofthenodewithapropertyvalue of 1 issettothenodewithavalueof 5: 

Let'stakealookatthemainmethodinthenextsection.

Themainmethod

Themainmethodaddsthenodeswithintegerpropertiesof 1,3,and5,asshowninthefollowingcode.Anodewithanintegerpropertyof 7 isaddedafterthenodewithanintegerpropertyof 1.The IterateListmethodisinvokedonthe linkedListinstance,asfollows:

//mainmethodfuncmain(){varlinkedListLinkedListlinkedList=LinkedList{}linkedList.AddToHead(1)linkedList.AddToHead(3)linkedList.AddToEnd(5)linkedList.AddAfter(1,7)linkedList.IterateList()}

Themainmethodadds1and3 totheheadofthelinkedlist.5isaddedtotheend.7isaddedafter1.Thelinkedlistwillbe3, 1,7,and 5.Runthefollowingcommandstoexecutethe linked_list.gofile:

gorunlinked_list.go

Afterexecutingtheprecedingcommand,wegetthefollowingoutput:

Let'stakealookatdoublylinkedlistinthenextsection.

DoublylinkedlistInadoublylinkedlist,allnodeshaveapointertothenodetheyareconnectedto,oneithersideofthem,inthelist.Thismeansthateachnodeisconnectedtotwonodes,andwecantraverseforwardthroughtothenextnodeorbackwardthroughtothepreviousnode.Doublylinkedlistsallowinsertion,deletionand,obviously,traversingoperations.Thenodeclassdefinitionispresentedinthefollowingcodeexample:

//NodeclasstypeNodestruct{propertyintnextNode*NodepreviousNode*Node}

Thefollowingsectionsexplaindoublylinkedlistmethods,suchasthe NodeBetweenValues,AddToHead,AddAfter,AddToEnd,andmainmethods.

TheNodeBetweenValuesmethod

TheNodeBetweenValuesmethodofthe LinkedListclassreturnsthenodethathasapropertylyingbetweenthe firstPropertyandsecondPropertyvalues.ThemethodtraversesthelisttofindoutwhetherthefirstPropertyandsecondPropertyintegerproperties matchonconsecutivenodes,asfollows:

//NodeBetweenValuesmethodofLinkedListfunc(linkedList*LinkedList)NodeBetweenValues(firstPropertyint,secondPropertyint)*Node{varnode*NodevarnodeWith*Nodefornode=linkedList.headNode;node!=nil;node=node.nextNode{ifnode.previousNode!=nil&&node.nextNode!=nil{ifnode.previousNode.property==firstProperty&&node.nextNode.property==secondProperty{nodeWith=nodebreak;}}}returnnodeWith}

Theexampleoutputafterthenodebetweenthevaluesmethodwasinvokedwith1and5 isshowninthefollowingscreenshot. ThenextNodeofthelastNodeissettothenodewithavalueof 5.Thenodewithapropertyvalueof 7isbetweenthenodeswithpropertyvaluesof 1and5:

Let'stakealookattheAddToHeadmethodinthenextsection.

TheAddToHeadmethod

TheAddToHeadmethodofthedoublyLinkedListclasssetsthepreviousNode propertyofthecurrentheadNode ofthelinkedlisttothenodethat'saddedwithproperty.Thenodewithpropertywillbesetasthe headNodeoftheLinkedList methodinthefollowingcode:

//AddToHeadmethodofLinkedListfunc(linkedList*LinkedList)AddToHead(propertyint){varnode=&Node{}node.property=propertynode.nextNode=niliflinkedList.headNode!=nil{node.nextNode=linkedList.headNodelinkedList.headNode.previousNode=node}linkedList.headNode=node}

Theexampleoutputafterthe  AddToHead methodwasinvokedwithproperty3 isasfollows.Anodewithproperty3iscreated.TheheadNode propertyofthelisthasapropertyvalueof 1.Thecurrentnodewithproperty3hasanextNode propertyof nil.ThenextNode propertyofthecurrentnodeissettoheadNodewithapropertyvalueof 1.ThepreviousnodeoftheheadNode propertyissettothecurrentnode:

Let'stakealookattheAddAftermethodinthenextsection.

AddAftermethod

TheAddAftermethodaddsanodeafteraspecificnodetoadoublelinkedlist.The AddAftermethodofthedoubleLinkedListclasssearchesthenodewhosevalueisequaltonodeProperty.ThefoundnodeissetasthepreviousNodeofthenodethatwasaddedwithproperty.ThenextNodeoftheaddednodewillbethe nodeWithproperty'snextNode.ThepreviousNodeoftheaddednodewillbethenodethatwasfoundwithvalueequalto nodeProperty.ThenodeWith nodewillbeupdatedtothecurrentnode. Inthefollowingcode,theAddAftermethodisshown:

//AddAftermethodofLinkedListfunc(linkedList*LinkedList)AddAfter(nodePropertyint,propertyint){varnode=&Node{}node.property=propertynode.nextNode=nilvarnodeWith*NodenodeWith=linkedList.NodeWithValue(nodeProperty)ifnodeWith!=nil{

node.nextNode=nodeWith.nextNodenode.previousNode=nodeWithnodeWith.nextNode=node}}

Theexampleoutputafterthe AddAfter methodisinvokedwithproperty7isasfollows.Anodewithpropertyvalue7iscreated.ThenextNode propertyofthecreatednodeisnil.ThenextNode propertyofthecreatednodeissettoheadNodewithpropertyvalue1.ThepreviousNode propertyof headNodeissettothecurrentnode:

Let'stakealookattheAddToEndmethodinthenextsection.

TheAddToEndmethod

TheAddToEndmethodaddsthenodetotheendofthedoublelinkedlist.TheAddToEndmethodofthe LinkedListclasscreatesanodewhosepropertyissetastheintegerparameterproperty.ThemethodsetsthepreviousNode propertyofthenodethatwasaddedwiththecurrentlastNode propertyasfollows.ThenextNodeofthecurrentlastNode propertyissettoanodeaddedwithpropertyattheendasfollows:

//AddToEndmethodofLinkedListfunc(linkedList*LinkedList)AddToEnd(propertyint){varnode=&Node{}node.property=propertynode.nextNode=nilvarlastNode*NodelastNode=linkedList.LastNode()iflastNode!=nil{

lastNode.nextNode=nodenode.previousNode=lastNode}}

Theexampleoutputafterthe AddToEnd methodwasinvokedwithproperty5isasfollows.Anodewithpropertyvalue5iscreated.ThelastNodeofthelisthaspropertyvalue1.ThenextNode propertyofthelastNodeisnil.ThenextNodeofthelastNodeissettothenodewithpropertyvalue5.ThepreviousNodeofthecreatednodeissettothenodewithpropertyvalue1:

Let'stakealookatthemainmethodinthenextsection.

Themainmethod

Inthefollowingcodesnippet,themainmethodcallstheNodeBetweenValues propertywithfirstPropertyandsecondProperty.Thenodepropertybetweenvalues1and5isprinted:

//mainmethodfuncmain(){varlinkedListLinkedListlinkedList=LinkedList{}linkedList.AddToHead(1)linkedList.AddToHead(3)linkedList.AddToEnd(5)linkedList.AddAfter(1,7)fmt.Println(linkedList.headNode.property)varnode*Nodenode=linkedList.NodeBetweenValues(1,5)fmt.Println(node.property)}

Themainmethodcreatesalinkedlist.Thenodesareaddedtotheheadandend.Thenodebetweenvalues1and5issearchedanditspropertyisprinted.Runthefollowingcommand toexecutethedoubly_linked_list.gofile:

gorundoubly_linked_list.go

Afterexecutingtheprecedingcommand,wegetthefollowingoutput:

Thenextsectiontalksaboutsets,whicharelineardatastructures.

SetsASetisalineardatastructurethathasacollectionofvaluesthatarenotrepeated.Asetcanstoreuniquevalueswithoutanyparticularorder.Intherealworld,setscanbeusedtocollectalltagsforblogpostsandconversationparticipantsinachat. ThedatacanbeofBoolean,integer,float,characters,andothertypes.Staticsetsallowonlyqueryoperations,whichmeansoperationsrelatedtoqueryingtheelements.Dynamicandmutablesetsallowfortheinsertionanddeletionofelements.Algebraicoperationssuchasunion,intersection,difference,andsubsetcanbedefinedonthesets.Thefollowingexampleshowsthe Set integerwithamap integerkeyandboolasavalue:

//mainpackagehasexamplesshown//inHands-OnDataStructuresandalgorithmswithGobookpackagemain//importingfmtpackageimport("fmt")//SetclasstypeSetstruct{integerMapmap[int]bool}//createthemapofintegerandboolfunc(set*Set)New(){set.integerMap=make(map[int]bool)}

TheAddElement,DeleteElement,ContainsElement,Intersect,Union,andmainmethodsarediscussedinthefollowingsections.

TheAddElementmethod

TheAddElementmethodaddstheelementtoaset.Inthefollowingcodesnippet,theAddElementmethodoftheSet classaddstheelementto integerMapiftheelementisnotintheSet.TheintegerMap elementhasthekeyintegerandvalueasbool,asshowninthefollowingcode:

//addstheelementtothesetfunc(set*Set)AddElement(elementint){if!set.ContainsElement(element){set.integerMap[element]=true}}

TheexampleoutputafterinvokingtheAddElementmethodwithparameter2isasfollows. Thecheckisdoneifthereisanelementwithvalue2.Ifthereisnoelement,themapissettotruewiththekeyas2:

Let'stakealookattheDeleteElementmethodinthenextsection.

TheDeleteElementmethod

TheDeleteElementmethoddeletestheelementfrom integerMapusingthedeletemethod.This methodremovestheelementfromthe integerMapoftheset,asfollows:

//deletestheelementfromthesetfunc(set*Set)DeleteElement(elementint){delete(set.integerMap,element)}

TheContainsElementmethod

TheContainsElementmethodoftheSetclasscheckswhetherornottheelementexistsin integerMap.TheintegerMap elementislookedupwithakeyintegerelement,asshowninthefollowingcodeexample:

//checksifelementisinthesetfunc(set*Set)ContainsElement(elementint)bool{varexistsbool_,exists=set.integerMap[element]returnexists}

Themainmethod–containselementInthefollowingcodesnippet,themainmethodcreates Set,invokestheNewmethod,andaddselements1and2.Thecheckisdoneifelement1existsintheset:

//mainmethodfuncmain(){varset*Setset=&Set{}set.New()set.AddElement(1)set.AddElement(2)fmt.Println(set)fmt.Println(set.ContainsElement(1))}

Runthefollowingcommandtoexecutetheset.gofile:gorunset.go

Afterexecutingtheprecedingcommand,wegetthefollowingoutput:

Let'stakealookattheInterSectmethodinthenextsection.

TheInterSectmethod

Inthefollowingcode,theInterSectmethodonthe SetclassreturnsanintersectionSetthatconsistsoftheintersectionofsetandanotherSet.Theset classistraversedthroughintegerMapandcheckedagainstanotherSet toseeifanyelementsexist:

//IntersectmethodreturnsthesetwhichintersectswithanotherSet

func(set*Set)Intersect(anotherSet*Set)*Set{varintersectSet=&Set{}intersectSet.New()varvalueintfor(value,_=rangeset.integerMap){ifanotherSet.ContainsElement(value){intersectSet.AddElement(value)}}returnintersectSet}

TheexampleoutputafterinvokingtheintersectwiththeparameterofanotherSetisasfollows.AnewintersectSetiscreated.Thecurrentsetisiteratedandeveryvalueischeckedtoseeifitisinanotherset.Ifthevalueisinanotherset,itisaddedtothe set intersect:

Let'stakealookattheUnionmethodinthenextsection.

TheUnionmethod

TheUnionmethodonthe SetclassreturnsaunionSetthatconsistsofaunionofsetandanotherSet.BothsetsaretraversedthroughintegerMapkeys,andunionsetisupdatedwithelementsfromthesets,asfollows:

//UnionmethodreturnsthesetwhichisunionofthesetwithanotherSet

func(set*Set)Union(anotherSet*Set)*Set{varunionSet=&Set{}unionSet.New()varvalueintfor(value,_=rangeset.integerMap){unionSet.AddElement(value)}

for(value,_=rangeanotherSet.integerMap){unionSet.AddElement(value)}

returnunionSet}

Theexampleoutputafterinvokingtheunionmethodwiththe anotherSet parameterisasfollows. AnewunionSetiscreated.Thecurrentsetandanothersetvaluesareiterated.Everyvalueisaddedtotheunionset:

Let'stakealookatthemainmethodinthenextsection.

Themainmethod–intersectionandunion

Inthefollowingcodesnippet,themainmethodcallsintersectanduniononthesetclass,passingtheanotherSet parameter.Theintersectionandunionsetsareprintedasfollows:

//mainmethodfuncmain(){varset*Setset=&Set{}set.New()set.AddElement(1)set.AddElement(2)fmt.Println("initialset",set)fmt.Println(set.ContainsElement(1))varanotherSet*SetanotherSet=&Set{}anotherSet.New()anotherSet.AddElement(2)anotherSet.AddElement(4)anotherSet.AddElement(5)fmt.Println(set.Intersect(anotherSet))fmt.Println(set.Union(anotherSet))}

Themainmethodtakestwosetsandfindstheintersectionandunionofthesets.Runthefollowingcommandtoexecutetheset.gofile:

gorunset.go

Afterexecutingtheprecedingcommand,wegetthefollowingoutput:

Thenextsectiontalksabouttuples,whicharefiniteorderedsequencesofobjects.

TuplesTuplesarefiniteorderedsequencesofobjects.Theycancontainamixtureofotherdatatypesandareusedtogrouprelateddataintoadatastructure.Inarelationaldatabase,atupleisarowofatable.Tupleshaveafixedsizecomparedtolists,andarealsofaster. Afinitesetoftuplesintherelationaldatabaseisreferredtoasarelationinstance.Atuplecanbeassignedinasinglestatement,whichisusefulforswappingvalues. Listsusuallycontainvaluesofthesamedatatype,whiletuplescontaindifferentdata.Forexample,wecanstoreaname,age,andfavoritecolorofauserinatuple. TupleswerecoveredinChapter1,DataStructuresandAlgorithms.Thefollowingsampleshowsamulti-valuedexpressionfromafunction'scall(tuples.go):

//mainpackagehasexamplesshown//inHands-OnDataStructuresandalgorithmswithGobookpackagemain//importingfmtpackageimport("fmt")//hfunctionwhichreturnstheproductofparametersxandyfunch(xint,yint)int{returnx*y}//gfunctionwhichreturnsxandyparametersaftermodificationfuncg(lint,mint)(xint,yint){x=2*ly=4*mreturn}//mainmethodfuncmain(){fmt.Println(h(g()))}

Themainfunctioncallsthe hfunctionwiththegfunctionasitsparameter.The gfunctionreturnsthe  tuplex andyintegers.Runthefollowingcommandtoexecutethetuples.gofile:

goruntuples.go

Afterexecutingtheprecedingcommand,wegetthefollowingoutput:

Thenextsectiontalksaboutqueues,whicharelineardatastructures.

QueuesAqueueconsistsofelementstobeprocessedinaparticularorderorbasedonpriority.Apriority-basedqueueofordersisshowninthefollowingcode,structuredasaheap.Operationssuchasenqueue,dequeue,andpeekcanbeperformedonqueue.Aqueueisalineardatastructureandasequentialcollection.Elementsareaddedtotheendandareremovedfromthestartofthecollection.Queuesarecommonlyusedforstoringtasksthatneedtobedone,orincomingHTTPrequeststhatneedtobeprocessedbyaserver.Inreallife,handlinginterruptionsinreal-timesystems,callhandling,andCPUtaskschedulingaregoodexamplesforusingqueues.ThefollowingcodeshowsthequeueofOrdersandhowthe Queuetypeisdefined:

//Queue—ArrayofOrdersTypetypeQueue[]*Order

//OrderclasstypeOrderstruct{priorityintquantityintproductstringcustomerNamestring}

Thefollowingsectionsinthechapterdiscussthe New,Add,andmainmethodsofqueue.

TheNewmethod

TheNewmethodonthe Orderclassassignsthepropertiesfromthe priority,quantity,and product parametersfornameandcustomerName.Themethodinitializesthepropertiesoftheorderasfollows:

//NewmethodinitializeswithOrderwithpriority,quantity,product,customerNamefunc(order*Order)New(priorityint,quantityint,productstring,customerNamestring){order.priority=priorityorder.quantity=quantityorder.product=productorder.customerName=customerName}

TheAddmethod

Inthefollowingcodesnippet,theAddmethodonthe Queueclasstakestheorderparameterandaddsit to Queuebasedonthepriority.Basedonthis,thelocationoftheorder parameterisfoundbycomparingitwiththepriority parameter:

//Addmethodaddstheordertothequeuefunc(queue*Queue)Add(order*Order){iflen(*queue)==0{*queue=append(*queue,order)}else{varappendedboolappended=falsevariintvaraddedOrder*Orderfori,addedOrder=range*queue{iforder.priority>addedOrder.priority{*queue=append((*queue)[:i],append(Queue{order},(*queue)[i:]...)...)appended=truebreak}}if!appended{*queue=append(*queue,order)}}}

Theexampleoutputaftertheaddmethodisinvokedwiththeorder parameterisasfollows. Theorderischeckedtoseewhetherornotitexistsinthequeue.Theorderisthenappendedtothequeue:

Let'stakealookattheMainmethodinthenextsection.

Themainmethod–queuesThemainmethodcreatestwoorders,andthepriorityoftheordersissetto2and1.Inthefollowingcode,thequeuewillfirstprocesstheorderwiththehighernumberonthepriorityvalue:

//mainmethodfuncmain(){varqueueQueuequeue=make(Queue,0)varorder1*Order=&Order{}varpriority1int=2varquantity1int=20varproduct1string="Computer"varcustomerName1string="GregWhite"order1.New(priority1,quantity1,product1,customerName1)varorder2*Order=&Order{}varpriority2int=1varquantity2int=10varproduct2string="Monitor"varcustomerName2string="JohnSmith"order2.New(priority2,quantity2,product2,customerName2)queue.Add(order1)

queue.Add(order2)

variint

fori=0;i<len(queue);i++{

fmt.Println(queue[i])

}

}

Runthefollowingcommands toexecutethe queue.gofile:gorunqueue.go

Afterexecutingtheprecedingcommand,wegetthefollowingoutput:

Let'stakealookatSynchronizedqueueinthenextsection.

SynchronizedqueueAsynchronizedqueueconsistsofelements thatneedtobeprocessedinaparticularsequence.Passengerqueueandticketprocessingqueuesaretypesofsynchronized queues,asfollows:

//mainpackagehasexamplesshown//inHands-OnDataStructuresandalgorithmswithGobookpackagemain//importingfmtpackageimport("fmt""time""math/rand")//constantsconst(messagePassStart=iotamessageTicketStartmessagePassEndmessageTicketEnd)//QueueclasstypeQueuestruct{waitPassintwaitTicketintplayPassboolplayTicketboolqueuePasschanintqueueTicketchanintmessagechanint}

Wewilldiscussthedifferentmethodsofsynchronizedqueueinthefollowingsections.

TheNewmethod

TheNewmethodonQueueinitializes message,queuePass,andqueueTicketwithnilvalues.ThemakemethodcreatesaQueuewitha chanintegerparameter, asfollows:

//Newmethodinitializesqueuefunc(queue*Queue)New(){queue.message=make(chanint)queue.queuePass=make(chanint)queue.queueTicket=make(chanint)}

Inthefollowingcodeexample,theGoroutinehandlesselectingthemessagebasedonthetypeofmessageandtherespectivequeuetoprocessit:

gofunc(){varmessageintfor{select{casemessage=<-queue.message:switchmessage{casemessagePassStart:queue.waitPass++casemessagePassEnd:queue.playPass=falsecasemessageTicketStart:queue.waitTicket++casemessageTicketEnd:queue.playTicket=false}ifqueue.waitPass>0&&queue.waitTicket>0&&!queue.playPass&&!queue.playTicket{queue.playPass=truequeue.playTicket=truequeue.waitTicket--queue.waitPass--queue.queuePass<-1queue.queueTicket<-1}}}}()}

TheStartTicketIssuemethod TheStartTicketIssuemethodstartstheissuingofaticketforpassengersstandinginaqueue.The StartTicketIssuemethodonQueuesendsmessageTicketStarttothemessage queueandqueueTicketreceivesthemessage.Theticketissueisstartedbysendingmessagestothequeue,asfollows:

//StartTicketIssuestartstheticketissuefunc(Queue*Queue)StartTicketIssue(){Queue.message<-messageTicketStart<-Queue.queueTicket}

TheEndTicketIssuemethod

TheEndTicketIssuemethodfinishestheissuingofatickettoapassengerstandinginthequeue.Inthefollowingcode,theEndTicketIssuemethodonQueuesendsmessageTicketEndtothemessage queue.Theticketissueisendedbysendingthemessage:

//EndTicketIssueendstheticketissuefunc(Queue*Queue)EndTicketIssue(){Queue.message<-messageTicketEnd}

TheticketIssuemethod

TheticketIssuemethodstartsandfinishestheissuingofatickettothepassenger.The ticketIssuemethodinvokesthe StartTicketIssue andEndTicketIssue methodsafterSleepcallsfor10secondsandtwoseconds.Theticketisissuedaftertheticketisprocessed,asshowninthefollowingcode:

//ticketIssuestartsandendstheticketissuefuncticketIssue(Queue*Queue){for{//Sleepupto10seconds.time.Sleep(time.Duration(rand.Intn(10000))*time.Millisecond)Queue.StartTicketIssue()fmt.Println("TicketIssuestarts")//Sleepupto2seconds.time.Sleep(time.Duration(rand.Intn(2000))*time.Millisecond)fmt.Println("TicketIssueends")Queue.EndTicketIssue()}}

TheStartPassmethod

TheStartPassmethodstartsthepassengerqueuemovingtowardtheticketcounter.TheStartPassmethodonQueuesendsmessagePassStarttothemessagequeueandqueuePassreceivesthemessage.Passengersaremovedintothequeueasfollows:

//StartPassendsthePassQueuefunc(Queue*Queue)StartPass(){Queue.message<-messagePassStart<-Queue.queuePass}

TheEndPassmethod

TheEndPassmethodstopsthepassengerqueuemovingtowardtheticketcounter.TheEndPassmethodonQueuesendsmessagePassEndtothemessagequeueinthefollowingcode.Thepassengerismovedtothecounterforticketprocessing,andthepassengeristhenoutofthequeue:

//EndPassendsthePassQueuefunc(Queue*Queue)EndPass(){Queue.message<-messagePassEnd}

Thepassengermethod

Thepassengermethodsstartsandendspassengermovementtothequeue.Thepassengermethodinvokesthe StartPass method,andthe EndPassmethodendsaftersleepcallsfor10secondsandtwoseconds.Thepassengermovesintothequeueandreachestheticketcounter,asshowninthefollowingcode:

//passengermethodstartsandendsthepassQueuefuncpassenger(Queue*Queue){//fmt.Println("startingthepassengerQueue")for{//fmt.Println("startingtheprocessing")//Sleepupto10seconds.time.Sleep(time.Duration(rand.Intn(10000))*time.Millisecond)Queue.StartPass()fmt.Println("Passengerstarts")//Sleepupto2seconds.time.Sleep(time.Duration(rand.Intn(2000))*time.Millisecond)fmt.Println("Passengerends")Queue.EndPass()}}

Themainmethod

ThemainmethodcallsthepassengerandticketIssuemethodsaftercreatingaqueue.Thepassengerentersintothequeueandaticketisissuedatthecounterintheprocessing queue,asexplainedinthefollowingcode:

//mainmethodfuncmain(){varQueue*Queue=&Queue{}//fmt.Println(Queue)Queue.New()fmt.Println(Queue)variintfori=0;i<10;i++{//fmt.Println(i,"passengerintheQueue")gopassenger(Queue)}//close(Queue.queuePass)varjintforj=0;j<5;j++{//fmt.Println(i,"ticketissuedintheQueue")goticketIssue(Queue)}select{}}

Runthefollowingcommand toexecutethe sync_queue.gofile:gorunsync_queue.go

Afterexecutingtheprecedingcommand,wegetthefollowingoutput:

ThenextsectiontalksaboutStacks,whicharelineardatastructures.

StacksAstackisalastin,firstoutstructureinwhichitemsareaddedfromthetop. Stacksareusedinparsersforsolvingmazealgorithms. Push,pop,top,andgetsizearethetypicaloperationsthatareallowedonstackdatastructures.Syntaxparsing,backtracking,andcompilingtimememorymanagementaresomereal-lifescenarioswherestackscanbeused.Anexampleofstackimplementationisasfollows(stack.go):

//mainpackagehasexamplesshown//inHands-OnDataStructuresandalgorithmswithGobookpackagemain//importingfmtpackageimport("fmt""strconv")//ElementclasstypeElementstruct{elementValueint}//StringmethodonElementclassfunc(element*Element)String()string{returnstrconv.Itoa(element.elementValue)}

TheElementclasshaselementValueasanattribute.TheString methodreturnstheelement'selementValue.Stacksmethods,suchasNew,Push,Pop,andmain arepresentedinthefollowingsections.

TheNewmethod

TheNewmethodonthe Stackclasscreatesadynamicarrayofelements.TheStackclasshasthecountandarraypointerofelements.ThecodesnippetwiththeStackclassdefinitionandthe Newmethodisasfollows:

//NewStackreturnsanewstack.func(stack*Stack)New(){stack.elements=make(*Element[]elements,0)}//StackisabasicLIFOstackthatresizesasneeded.typeStackstruct{elements[]*ElementelementCountint}

ThePushmethod

ThePushmethodaddsthenodetothetopofthestack class.Inthefollowingcodesample,the Pushmethodonthe Stackclassaddstheelementtotheelementsarrayandincreasesthe Count element,whiletheappendmethodaddstheelementtotheelementsofthestack class:

//Pushaddsanodetothestack.func(stack*Stack)Push(element*Element){stack.elements=append(stack.elements[:stack.elementCount],element)stack.elementCount=stack.elementCount+1}

Theexampleoutputafterthepushmethodisinvokedwithparameterelementsasfollows.Theelementwiththevalue7ispushedtothestack.Thecountoftheelementsbeforepushingtothestackis2,and,afterpushingtothestack,thisfigureis3:

Let'stakealookatthePopmethodinthenextsection.

ThePopmethod

ThePopmethodonthe Stackimplementationremovesthelastelementfromtheelementarrayandreturnstheelement,asshowninthefollowingcode.Thelenmethodreturnsthelengthoftheelementsarray:

//Popremovesandreturnsanodefromthestackinlasttofirstorder.func(stack*Stack)Pop()*Element{ifstack.elementCount==0{returnnil}varlengthint=len(stack.elements)varelement*Element=stack.elements[length-1]//stack.elementCount=stack.elementCount-1iflength>1{stack.elements=stack.elements[:length-1]}else{stack.elements=stack.elements[0:]}stack.elementCount=len(stack.elements)returnelement}

TheexampleoutputafterthePopmethodisinvokedisasfollows.Theelementvalue5ispassedandaddedtothe Pop method.ThecountofelementsbeforeinvokingthePopmethodis2.Thecountoftheelementsaftercallingthe Popmethodis1:

Let'stakealookatthemainmethodinthenextsection.

Themainmethod

Inthefollowingcodesection,themainmethodcreatesastack,callstheNewmethod,andpushestheelementsafterinitializingthem.Thepopped-outelementvalueandtheorderisprinted:

//mainmethodfuncmain(){varstack*Stack=&Stack{}stack.New()varelement1*Element=&Element{3}varelement2*Element=&Element{5}varelement3*Element=&Element{7}varelement4*Element=&Element{9}stack.Push(element1)stack.Push(element2)stack.Push(element3)stack.Push(element4)fmt.Println(stack.Pop(),stack.Pop(),stack.Pop(),stack.Pop())}

Runthefollowingcommands toexecutethestack.gofile:gorunstack.go

Afterexecutingtheprecedingcommand,wegetthefollowingoutput:

SummaryThischaptercoveredthedefinitionofLinkedList,doubleLinkedList,Tuples,Sets,Queues,andStacks.The LinkedListmethods– AddToHead,AddToEnd,LastNode,anditerateList—werealsocoveredinthischapter.Inaddition,apriorityqueuewasmodeledasaheapoforderstobeprocessed,syncqueuewaspresentedaspassengerandticketprocessingqueues,andtupleswereexplainedinacontextinwhichafunctionreturnsamultivaluedexpression.Thenew,push,pop,andstringmethodsforStack wereexplainedwithcodesamples.Inthenextchapter,wewillcoverareassuchasthe Trees,Tables,Containers,andHashfunctions.

Questions1. Wherecanyouusedoublelinkedlist?Pleaseprovideanexample.2. Whichmethodonlinkedlistcanbeusedforprintingoutnodevalues?3. WhichqueuewasshownwithchannelsfromtheGolanguage?4. Writeamethodthatreturnsmultiplevalues.Whatdatastructurecanbeusedforreturningmultiplevalues?

5. Cansethaveduplicateelements?6. Writeacode sampleshowingtheunionandintersectionoftwosets.7. Inalinkedlist,whichmethodisusedtofindthenodebetweentwovalues?

8. Wehaveelementsthatarenotrepeatedandunique.Whatisthecorrectdatastructurethatrepresentsthecollection?

9. InGo,howdoyougeneratearandomintegerbetweenthevalues3and5?

10. Whichmethodiscalledtocheckifanelementofvalue5existsintheSet?

Furtherreading

ToreadmoreaboutLinkedLists,Sets,Tuples,andStacks,consultthefollowingsources:

DesignPatterns, byErichGamma,RichardHelm,RalphJohnson,andJohnVlissidesIntroductiontoAlgorithms –ThirdEdition,byThomasH.Cormen,CharlesE.Leiserson,RonaldL.Rivest,andCliffordSteinDatastructuresandAlgorithms:AnEasyIntroduction,by RudolphRussell

Non-LinearDataStructuresNon-lineardatastructuresareusedincryptographyandotherareas.Anon-lineardatastructureisanarrangementinwhichanelementis connectedtomanyelements.Thesestructuresusememoryquicklyandefficiently.Freecontiguousmemoryisnotrequiredforaddingnewelements.Thelengthofthedatastructuresisnotimportantbeforeaddingnewelements.Anon-lineardatastructurehasmultiplelevelsandalinearonehasasinglelevel.Thevaluesoftheelementsarenotorganizedinanon-lineardatastructure.Thedataelementsinanon-lineardatastructurecannotbeiteratedinonestep.Theimplementationofthesedatastructuresiscomplicated.Treetypessuchasbinarysearchtrees,treaps,andsymboltablesareexplainedinthischapter. Thischaptercoversthefollowingnon-lineardatastructures:

TreesTablesContainersHashfunctions

TechnicalrequirementsInstallGoversion1.10fromhttps://golang.org/doc/install foryourOS.TheGitHubURLforthecodeinthischapterisasfollows: https://github.com/PacktPublishing/Learn-Data-Structures-and-Algorithms-with-Golang/tree/master/Chapter04.

TreesAtreeisanon-lineardatastructure. Treesareusedforsearchandotherusecases.Abinarytreehasnodesthathaveamaximumoftwochildren.Abinarysearchtreeconsistsofnodeswherethepropertyvaluesoftheleftnodearelessthanthepropertyvaluesoftherightnode.Therootnodeisatlevelzeroofatree.Eachchildnodecouldbealeaf.Treesandbinarytrees wereintroducedin Chapter1,DataStructuresandAlgorithms,whilewewerediscussinglogarithmiccomplexity. Let'stakeacloserlookattheminthenextsection.

BinarysearchtreeAbinarysearchtreeisadatastructurethatallowsforthequicklookup,addition,andremovalofelements.Itstoresthekeysinasortedordertoenableafasterlookup.Thisdatastructurewasinventedby P.F.Windley,A.D.Booth,A.J.T.Colin,andT.N.Hibbard.Onaverage,spaceusageforabinarysearchtreeisoftheorderO(n),whereastheinsert,search,anddeleteoperationsareoftheorderO(logn). Abinarysearchtreeconsistsofnodes withpropertiesorattributes:

AkeyintegerAvalueintegerTheleftNodeandrightNodeinstances of TreeNode

Theycanberepresentedinthefollowingcode://TreeNodeclasstypeTreeNodestruct{keyintvalueintleftNode*TreeNoderightNode*TreeNode}

Inthenextsection,the BinarySearchTreeclassimplementationisdiscussed.Forthissection,pleaserefertothebinary_search_tree.gofile.

TheBinarySearchTreeclassInthefollowingcodesnippet,theBinarySearchTreeclassconsistsofa rootNodethat'softheTreeNodetype,andlock,whichisofthesync.RWMutextype.ThebinarysearchtreeistraversedfromrootNodebyaccessingthenodestotheleftandright ofrootNode:

//BinarySearchTreeclasstypeBinarySearchTreestruct{rootNode*TreeNodelocksync.RWMutex}

Nowthatweknowwhat BinarySearchTreeis,let'stakealookatitsdifferentmethodsinthenextsection. 

TheInsertElementmethod

TheInsertElementmethodinsertstheelementwiththegivenkeyandvalueinthebinarysearchtree.Thetree'slock()instanceislockedfirstandtheunlock()methodisdeferredbeforeinsertingtheelement.TheInsertTreeNodemethodisinvokedbypassingrootNodeandthenodetobecreatedwiththekeyandvalue,asshownhere:

//InsertElementmethodfunc(tree*BinarySearchTree)InsertElement(keyint,valueint){tree.lock.Lock()defertree.lock.Unlock()vartreeNode*TreeNodetreeNode=&TreeNode{key,value,nil,nil}iftree.rootNode==nil{tree.rootNode=treeNode}else{insertTreeNode(tree.rootNode,treeNode)}}

Theexampleoutputforinsertinganelementwithkeyandvalue3isshownasfollows.TheinsertelementmethodcallsinsertTreeNodewithrootNode withkey8andthenewtreeNodewithkey3:

TheinsertTreeNodemethod

TheinsertTreenodemethodinsertsthenewTreeNodeinthebinarysearchtree. Inthefollowingcode,theinsertTreeNodemethodtakesrootNodeandnewTreeNode,bothoftheTreeNodetype,asparameters.Notethat newTreeNodeisinsertedattherightplaceinthebinarysearchtreebycomparingthekeyvalues:

//insertTreeNodefunctionfuncinsertTreeNode(rootNode*TreeNode,newTreeNode*TreeNode){ifnewTreeNode.key<rootNode.key{ifrootNode.leftNode==nil{rootNode.leftNode=newTreeNode}else{insertTreeNode(rootNode.leftNode,newTreeNode)}}else{ifrootNode.rightNode==nil{rootNode.rightNode=newTreeNode}else{insertTreeNode(rootNode.rightNode,newTreeNode)}}}

TheinOrderTraversemethod

TheinOrderTraversemethodvisitsallnodes inorder.TheRLock() methodonthetree lockinstanceiscalledfirst.TheRUnLock()methodisdeferredonthetree lockinstancebeforeinvokingtheinOrderTraverseTreemethod,aspresentedinthefollowingcodesnippet:

//InOrderTraverseTreemethodfunc(tree*BinarySearchTree)InOrderTraverseTree(functionfunc(int)){tree.lock.RLock()defertree.lock.RUnlock()inOrderTraverseTree(tree.rootNode,function)}

TheinOrderTraverseTreemethod

TheinOrderTraverseTreemethodtraversestheleft,theroot,andtherighttree.TheinOrderTraverseTreemethodtakestreeNodeoftheTreeNodetypeand functionasparameters.TheinOrderTraverseTreemethodiscalledonleftNodeandrightNodewithfunctionasaparameter.AfunctionispassedwithtreeNode.value,asshowninthefollowingcodesnippet:

//inOrderTraverseTreemethodfuncinOrderTraverseTree(treeNode*TreeNode,functionfunc(int)){iftreeNode!=nil{inOrderTraverseTree(treeNode.leftNode,function)function(treeNode.value)inOrderTraverseTree(treeNode.rightNode,function)}}

ThePreOrderTraverseTreemethod

ThePreOrderTraverseTreemethodvisitsallthe treenodeswithpreordertraversing.Thetree lockinstanceislockedfirstandtheUnlockmethodisdeferredbeforepreOrderTraverseTreeiscalled.Inthefollowingcodesnippet,thepreOrderTraverseTreemethodispassedwithrootNodeandfunctionasparameters:

//PreOrderTraverseTreemethodfunc(tree*BinarySearchTree)PreOrderTraverseTree(functionfunc(int)){tree.lock.Lock()defertree.lock.Unlock()preOrderTraverseTree(tree.rootNode,function)}

ThepreOrderTraverseTreemethod

ThepreOrderTraverseTreemethodispassedwithtreeNodeoftheTreeNodetypeandfunctionasparameters.ThepreOrderTraverseTreemethodiscalledbypassingleftNodeandrightNodewithfunctionasparameters.The function isinvokedwithtreeNode.value,asshownhere:

//preOrderTraverseTreemethodfuncpreOrderTraverseTree(treeNode*TreeNode,functionfunc(int)){iftreeNode!=nil{function(treeNode.value)preOrderTraverseTree(treeNode.leftNode,function)preOrderTraverseTree(treeNode.rightNode,function)}}

ThePostOrderTraverseTreemethod

ThePostOrderTraverseTreemethodtraversesthenodesinapostorder(left,right,currentnode).Inthefollowingcodesnippet,thePostOrderTraverseTreemethodoftheBinarySearchTreeclassvisitsallnodeswithpost-ordertraversing.Thefunction methodispassedasaparametertothemethod.Thetree.lockinstanceislockedfirstandtheUnlockmethodisdeferredonthetree lockinstancebeforecallingthepostOrderTraverseTreemethod:

//PostOrderTraverseTreemethodfunc(tree*BinarySearchTree)PostOrderTraverseTree(functionfunc(int)){tree.lock.Lock()defertree.lock.Unlock()postOrderTraverseTree(tree.rootNode,function)}

ThepostOrderTraverseTreemethod

ThepostOrderTraverseTreemethodispassedwithtreeNodeoftheTreeNodetypeandfunctionasparameters.ThepostOrderTraverseTreemethodiscalledbypassingleftNodeandrightNodewithfunctionasparameters.Inthefollowingcodesnippet,functionisinvokedwithtreeNode.valueasaparameter:

//postOrderTraverseTreemethodfuncpostOrderTraverseTree(treeNode*TreeNode,functionfunc(int)){iftreeNode!=nil{postOrderTraverseTree(treeNode.leftNode,function)postOrderTraverseTree(treeNode.rightNode,function)function(treeNode.value)}}

TheMinNodemethod

MinNodefindsthenodewiththeminimumvalueinthebinarysearchtree. Inthefollowingcodesnippet,theRLockmethodofthetree lockinstanceisinvokedfirstandtheRUnlockmethodonthetree lockinstanceisdeferred.TheMinNodemethodreturnstheelementwiththelowestvaluebytraversingfromrootNodeandcheckingwhetherthevalueofleftNodeisnil:

//MinNodemethodfunc(tree*BinarySearchTree)MinNode()*int{tree.lock.RLock()defertree.lock.RUnlock()vartreeNode*TreeNodetreeNode=tree.rootNodeiftreeNode==nil{//nilinsteadof0return(*int)(nil)}for{iftreeNode.leftNode==nil{return&treeNode.value}treeNode=treeNode.leftNode}}

TheMaxNodemethod

MaxNodefindsthenodewithmaximumpropertyinthebinarysearchtree. TheRLockmethodofthetree lockinstanceiscalledfirstandtheRUnlockmethodonthetree lockinstanceisdeferred.TheMaxNodemethodreturnstheelementwiththehighestvalueaftertraversingfromrootNodeandfindingarightNodewithanilvalue.Thisisshowninthefollowingcode:

//MaxNodemethodfunc(tree*BinarySearchTree)MaxNode()*int{tree.lock.RLock()defertree.lock.RUnlock()vartreeNode*TreeNodetreeNode=tree.rootNodeiftreeNode==nil{//nilinsteadof0return(*int)(nil)}for{iftreeNode.rightNode==nil{return&treeNode.value}treeNode=treeNode.rightNode}}

TheSearchNodemethod

TheSearchNodemethodsearchesthespecifiednodeinthebinarysearchtree.First,theRLockmethodofthetreelockinstanceiscalled.Then,theRUnlockmethodonthetree lockinstanceisdeferred.TheSearchNodemethodoftheBinarySearchTreeclassinvokesthesearchNodemethodwiththerootNodeandthe keyintegervalueas parameters, asshownhere:

//SearchNodemethodfunc(tree*BinarySearchTree)SearchNode(keyint)bool{tree.lock.RLock()defertree.lock.RUnlock()returnsearchNode(tree.rootNode,key)}

ThesearchNodemethod

Inthefollowingcode,thesearchNodemethodtakestreeNode,apointeroftheTreeNodetype,andakeyintegervalueasparameters.Themethodreturnstrueorfalseaftercheckingwhether treeNodewiththesamevalueas keyexists:

//searchNodemethodfuncsearchNode(treeNode*TreeNode,keyint)bool{iftreeNode==nil{returnfalse}ifkey<treeNode.key{returnsearchNode(treeNode.leftNode,key)}ifkey>treeNode.key{returnsearchNode(treeNode.rightNode,key)}returntrue}

TheRemoveNodemethod

TheRemoveNodemethodoftheBinarySearchTreeclassremovestheelementwith keythat'spassedin.Themethodtakesthekeyintegervalueastheparameter.TheLock()methodisinvokedonthetree'slockinstancefirst.TheUnlock()methodofthetree lockinstanceisdeferred,andremoveNodeiscalledwithrootNodeandthekeyvalueasparameters,asshownhere:

//RemoveNodemethodfunc(tree*BinarySearchTree)RemoveNode(keyint){tree.lock.Lock()defertree.lock.Unlock()removeNode(tree.rootNode,key)}

TheremoveNodemethod

TheremoveNodemethodtakestreeNodeoftheTreeNodetypeanda keyintegervalueasparameters.Inthefollowingcodesnippet,themethodrecursivelysearchesthe leftNodeinstanceoftreeNodeandthekeyvalueofrightNode ifitmatchestheparametervalue:

//removeNodemethodfuncremoveNode(treeNode*TreeNode,keyint)*TreeNode{iftreeNode==nil{returnnil}ifkey<treeNode.key{treeNode.leftNode=removeNode(treeNode.leftNode,key)returntreeNode}ifkey>treeNode.key{treeNode.rightNode=removeNode(treeNode.rightNode,key)returntreeNode}//key==node.keyiftreeNode.leftNode==nil&&treeNode.rightNode==nil{treeNode=nilreturnnil}iftreeNode.leftNode==nil{treeNode=treeNode.rightNodereturntreeNode}iftreeNode.rightNode==nil{treeNode=treeNode.leftNodereturntreeNode}varleftmostrightNode*TreeNodeleftmostrightNode=treeNode.rightNodefor{//findsmallestvalueontherightsideifleftmostrightNode!=nil&&leftmostrightNode.leftNode!=nil{leftmostrightNode=leftmostrightNode.leftNode}else{break}}treeNode.key,treeNode.value=leftmostrightNode.key,leftmostrightNode.valuetreeNode.rightNode=removeNode(treeNode.rightNode,treeNode.key)returntreeNode}

TheStringmethod

TheStringmethodturnsthetreeintoastringformat. Atfirst,theLock()methodisinvokedonthetree lockinstance.Then,theUnlock()methodofthetree lockinstanceisdeferred.TheStringmethodprintsavisualrepresentationoftree:

//Stringmethodfunc(tree*BinarySearchTree)String(){tree.lock.Lock()defertree.lock.Unlock()fmt.Println("------------------------------------------------")stringify(tree.rootNode,0)fmt.Println("------------------------------------------------")}

Thestringifymethod

Inthefollowingcodesnippet,thestringifymethodtakesatreeNodeinstanceoftheTreeNodetypeandlevel (an integer)asparameters.Themethodrecursivelyprintsthetreebasedonthelevel:

//stringifymethodfuncstringify(treeNode*TreeNode,levelint){iftreeNode!=nil{format:=""fori:=0;i<level;i++{format+=""}format+="---["level++stringify(treeNode.leftNode,level)fmt.Printf(format+"%d\n",treeNode.key)stringify(treeNode.rightNode,level)}}

Themainmethod

Inthefollowingcode,themainmethodcreatesthebinarysearchtreeandinsertstheelements8,3,10,1,and6intoit.treeisprintedbyinvokingtheStringmethod:

//mainmethodfuncmain(){vartree*BinarySearchTree=&BinarySearchTree{}tree.InsertElement(8,8)tree.InsertElement(3,3)tree.InsertElement(10,10)tree.InsertElement(1,1)tree.InsertElement(6,6)tree.String()}

Runthefollowingcommandtoexecutethebinary_search_tree.gofile:gorunbinary_search_tree.go

Theoutputisasfollows:

ThenextsectiontalksaboutAVLtreeimplementation.

Adelson,Velski,andLandis(AVL)treeAdelson,Velski,andLandispioneeredtheAVLtreedatastructureandhenceitisnamedafterthem.Itconsistsofheightadjustingbinarysearchtrees.Thebalancefactorisobtainedbyfindingthedifferencebetweentheheightsoftheleftandrightsub-trees. Balancingisdoneusingrotationtechniques.Ifthebalancefactorisgreaterthanone,rotationshiftsthenodestotheoppositeoftheleftorrightsub-trees.Thesearch,addition,anddeletionoperationsareprocessedintheorderofO(log n).Thefollowingsectionstalksaboutthe KeyValue interfacedefinitionandthe TreeNodeclass. Forthissection,pleaserefertotheavl_tree.gofile.

TheKeyValueinterfaceTheKeyValueinterfacehasthe LessThanandEqualTomethods.TheLessThanandEqualTomethodstakeKeyValueasaparameterandreturnaBooleanvalueaftercheckingthelessthanorequaltocondition.Thisisshowninthefollowingcode:

//KeyValuetypetypeKeyValueinterface{LessThan(KeyValue)boolEqualTo(KeyValue)bool}

TheTreeNodeclassTheTreeNodeclasshasKeyValue,BalanceValue,andLinkedNodesasproperties.TheAVLtreeiscreatedasatreeofnodesoftheTreeNodetype,asshownhere:

//TreeNodeclasstypeTreeNodestruct{KeyValueKeyValueBalanceValueintLinkedNodes[2]*TreeNode}

Now,let'stakealookatthedifferentmethodsofthe TreeNodeclass.

Theoppositemethod

Theoppositemethodtakesanodevalueandreturnstheoppositenode'svalue.Inthefollowingcodesnippet,theoppositemethodtakesthenodeValueintegerasaparameterandreturnstheoppositenode'svalue:

//oppositemethodfuncopposite(nodeValueint)int{return1-nodeValue}

ThesingleRotationmethod

ThesingleRotationmethodrotatesthenodeoppositetothespecified sub-tree.Asshowninthefollowingsnippet,thesingleRotationfunctionrotatesthenode oppositetheleftorrightsub-tree.Themethodtakesthepointerto rootNodeandanodeValueinteger asparametersandreturnsaTreeNodepointer:

//singlerotationmethodfuncsingleRotation(rootNode*TreeNode,nodeValueint)*TreeNode{varsaveNode*TreeNodesaveNode=rootNode.LinkedNodes[opposite(nodeValue)]rootNode.LinkedNodes[opposite(nodeValue)]=saveNode.LinkedNodes[nodeValue]saveNode.LinkedNodes[nodeValue]=rootNodereturnsaveNode}

ThedoubleRotationmethod

Here,thedoubleRotationmethodrotatesthenodetwice.ThemethodreturnsaTreeNodepointer,takingparameterssuchasrootNode,whichisatreeNodepointer,andnodeValue,whichisaninteger.Thisisshowninthefollowingcode:

//doublerotationfuncdoubleRotation(rootNode*TreeNode,nodeValueint)*TreeNode{varsaveNode*TreeNodesaveNode=rootNode.LinkedNodes[opposite(nodeValue)].LinkedNodes[nodeValue]rootNode.LinkedNodes[opposite(nodeValue)].LinkedNodes[nodeValue]=saveNode.LinkedNodes[opposite(nodeValue)]saveNode.LinkedNodes[opposite(nodeValue)]=rootNode.LinkedNodes[opposite(nodeValue)]rootNode.LinkedNodes[opposite(nodeValue)]=saveNodesaveNode=rootNode.LinkedNodes[opposite(nodeValue)]rootNode.LinkedNodes[opposite(nodeValue)]=saveNode.LinkedNodes[nodeValue]saveNode.LinkedNodes[nodeValue]=rootNodereturnsaveNode}

TheimplementationofthismethodisshowninTheInsertNodemethodsection,asfollows.

TheadjustBalancemethod

TheadjustBalancemethodadjuststhebalanceofthetree.Inthefollowingcodesnippet,theadjustBalancemethoddoesadoublerotationgiventhebalancefactor,rootNode,andnodeValue.TheadjustBalancemethodtakesrootNode,whichisaninstanceoftheTreeNodetype,nodeValue,andbalanceValue(whicharebothintegers) asparameters:

//adjustbalancemethodfuncadjustBalance(rootNode*TreeNode,nodeValueint,balanceValueint){varnode*TreeNodenode=rootNode.LinkedNodes[nodeValue]varoppNode*TreeNodeoppNode=node.LinkedNodes[opposite(balanceValue)]switchoppNode.BalanceValue{case0:rootNode.BalanceValue=0node.BalanceValue=0casebalanceValue:rootNode.BalanceValue=-balanceValuenode.BalanceValue=0default:rootNode.BalanceValue=0node.BalanceValue=balanceValue}oppNode.BalanceValue=0}

TheBalanceTreemethod

TheBalanceTreemethodchangesthebalancefactorbyasingleordoublerotation.ThemethodtakesrootNode(aTreeNodepointer)andnodeValue (an integer)as parameters.TheBalanceTreemethodreturnsaTreeNodepointer,asshownhere:

//BalanceTreemethodfuncBalanceTree(rootNode*TreeNode,nodeValueint)*TreeNode{varnode*TreeNodenode=rootNode.LinkedNodes[nodeValue]varbalanceintbalance=2*nodeValue-1ifnode.BalanceValue==balance{rootNode.BalanceValue=0node.BalanceValue=0returnsingleRotation(rootNode,opposite(nodeValue))}adjustBalance(rootNode,nodeValue,balance)returndoubleRotation(rootNode,opposite(nodeValue))}

TheinsertRNodemethod

TheinsertRNodemethodinsertsthenodeandbalancesthetree.Thismethod inserts rootNodewiththe KeyValuekey,aspresentedinthefollowingcodesnippet.ThemethodtakesrootNode,whichisaTreeNodepointer,andthekeyasanintegeras parameters.ThemethodreturnsaTreeNodepointerandaBooleanvalueiftherootNodeisinserted:

//insertRNodemethodfuncinsertRNode(rootNode*TreeNode,keyKeyValue)(*TreeNode,bool){ifrootNode==nil{return&TreeNode{KeyValue:key},false}vardirintdir=0ifrootNode.KeyValue.LessThan(key){dir=1}vardoneboolrootNode.LinkedNodes[dir],done=insertRNode(rootNode.LinkedNodes[dir],key)ifdone{returnrootNode,true}rootNode.BalanceValue=rootNode.BalanceValue+(2*dir-1)switchrootNode.BalanceValue{case0:returnrootNode,truecase1,-1:returnrootNode,false}returnBalanceTree(rootNode,dir),true}

TheInsertNodemethod

TheInsertNodemethodinsertsanodeintotheAVLtree. This methodtakestreeNode,whichisadoubleTreeNodepointer,andthe keyvalueasparameters:

//InsertNodemethodfuncInsertNode(treeNode**TreeNode,keyKeyValue){*treeNode,_=insertRNode(*treeNode,key)}

Theexampleoutputofthe InsertNodemethodisshowninthefollowingscreenshot.TheInsertNodemethodcallsthe insertRNodemethodwiththe rootNode parametersandnodetobeinserted.rootNodehasakeyvalueof 5andthenodetobeinsertedhasakeyvalueof 6.Thetreeneedstobebalanced.Hence,thenextcallwillberootNodewithkey8andnodetobeinserted.Thenextstepcallsrootnodewithkeyvalue7andnodetobeinserted.ThelastcallwillbewithrootNodenilandnodetobeinserted.Thebalancevalueischeckedandthebalancetreemethodreturnsthebalancedtree:

TheRemoveNodemethod

Inthefollowingcode,theRemoveNodemethodremovestheelementfromtheAVLtreebyinvokingtheremoveRNodemethod.ThemethodtakestreeNode,whichisadoubleTreeNodepointer,and KeyValueas parameters:

//RemoveNodemethodfuncRemoveNode(treeNode**TreeNode,keyKeyValue){*treeNode,_=removeRNode(*treeNode,key)}

TheremoveBalancemethod

TheremoveBalancemethodremovesthebalancefactorinatree.This methodadjuststhebalancefactorafterremovingthenodeandreturnsatreeNodepointerandaBooleanifthebalanceisremoved.ThemethodtakesrootNode(aninstanceofTreeNode)andnodeValue(aninteger)asparameters.Thisisshowninthefollowingcode:

//removeBalancemethodfuncremoveBalance(rootNode*TreeNode,nodeValueint)(*TreeNode,bool){varnode*TreeNodenode=rootNode.LinkedNodes[opposite(nodeValue)]varbalanceintbalance=2*nodeValue-1switchnode.BalanceValue{case-balance:rootNode.BalanceValue=0node.BalanceValue=0returnsingleRotation(rootNode,nodeValue),falsecasebalance:adjustBalance(rootNode,opposite(nodeValue),-balance)returndoubleRotation(rootNode,nodeValue),false}rootNode.BalanceValue=-balancenode.BalanceValue=balancereturnsingleRotation(rootNode,nodeValue),true}

TheremoveRNodemethod

TheremoveRNode methodremovesthenodefromthetreeandbalancesthetree.This methodtakesrootNode,whichisaTreeNodepointer,andthe keyvalue.ThismethodreturnsaTreeNodepointerandBooleanvalueifRNode isremoved,asshowninthefollowingcodesnippet:

//removeRNodemethodfuncremoveRNode(rootNode*TreeNode,keyKeyValue)(*TreeNode,bool){ifrootNode==nil{returnnil,false}ifrootNode.KeyValue.EqualTo(key){switch{caserootNode.LinkedNodes[0]==nil:returnrootNode.LinkedNodes[1],falsecaserootNode.LinkedNodes[1]==nil:returnrootNode.LinkedNodes[0],false}varheirNode*TreeNodeheirNode=rootNode.LinkedNodes[0]forheirNode.LinkedNodes[1]!=nil{heirNode=heirNode.LinkedNodes[1]}rootNode.KeyValue=heirNode.KeyValuekey=heirNode.KeyValue}vardirintdir=0ifrootNode.KeyValue.LessThan(key){dir=1}vardoneboolrootNode.LinkedNodes[dir],done=removeR(rootNode.LinkedNodes[dir],key)ifdone{returnrootNode,true}rootNode.BalanceValue=rootNode.BalanceValue+(1-2*dir)switchrootNode.BalanceValue{case1,-1:returnrootNode,truecase0:returnrootNode,false}returnremoveBalance(rootNode,dir)}typeintegerKeyintfunc(kintegerKey)LessThan(k1KeyValue)bool{returnk<k1.(integerKey)}func(kintegerKey)EqualTo(k1KeyValue)bool{returnk==k1.(integerKey)}

Theexampleoutputofthe removeRNodemethodisshownasfollows.TheRemoveNodemethodcallstheremoveRNodemethod.TheremoveRNodemethod

RemoveNodemethodcallstheremoveRNodemethod.TheremoveRNodemethodtakestheparameters,suchasrootNodeandKeyValue,ofthenode:

Themainmethod

Inthefollowingcodesnippet,themainmethodcreatesanAVLtreebyinsertingnodeswiththe 5,3,8,7,6,and10 keys.Nodeswiththe 3and7 keysareremoved.ThetreedatastructureisconvertedintoJSONinbytes.TheJSONbytesareprintedafterbeingchangedtoastring:

//mainmethodfuncmain(){vartreeNode*TreeNodefmt.Println("Treeisempty")varavlTree[]byteavlTree,_=json.MarshalIndent(treeNode,"","")fmt.Println(string(avlTree))

fmt.Println("\nAddTree")InsertNode(&treeNode,integerKey(5))InsertNode(&treeNode,integerKey(3))InsertNode(&treeNode,integerKey(8))InsertNode(&treeNode,integerKey(7))InsertNode(&treeNode,integerKey(6))InsertNode(&treeNode,integerKey(10))avlTree,_=json.MarshalIndent(treeNode,"","")fmt.Println(string(avlTree))

fmt.Println("\nDeleteTree")RemoveNode(&treeNode,integerKey(3))RemoveNode(&treeNode,integerKey(7))avlTree,_=json.MarshalIndent(treeNode,"","")fmt.Println(string(avlTree))}

Runthefollowingcommandtoexecutetheavl_tree.gofile:gorunavl_tree.go

Theoutputisasfollows:

Inthenextsection,B+treeimplementationisdiscussedandcodesnippetsarepresented. 

B+treeTheB+treecontainsalistofkeysandpointerstothenext-levelnodesintrees.Duringasearch,recursionisusedtosearchforanelementbylookingforthe theadjacentnodekeys.B+treesareusedtostoredatainfilesystems.B+treesrequirefewerI/Ooperationstosearchforanodeinthetree.Fan-outisdefinedasthenumberofnodespointingtothechildnodesofanodeinaB+tree.B+treeswerefirst describedinatechnicalpaperby RudolfBayerandEdwardM.McCreight.Theblock-orientedstoragecontextinB+treeshelpswiththestorageandefficientretrievalofdata.Thespaceefficiencyofa B+treecanbeenhancedbyusingcompressiontechniques.B+treesbelongtoafamilyofmultiwaysearchtrees.Forab-orderB+tree,spaceusageisoftheorderO(n).Inserting,finding,andremovingoperationsareoftheorderO(logbn).

B-treeTheB-treeisasearchtreewithnon-leafnodesthatonly havekeys,andthedataisintheleaves.B-treesareusedtoreducethenumberofdiskaccesses.TheB-treeisaself-adjustingdatastructurethatkeepsdatasorted.B-treesstorekeysinasortedorderforeasytraversal.Theycanhandlemultiple insertionsanddeletions.Knuthinitiallycameupwiththeconceptofthisdatastructure.B-treesconsistofnodesthathaveatmostnchildren.Everynon-leafnodeinthetreehasatleastn/2childnodes. RudolfBayerandEdwardM.McCreightwerethefirsttoimplementthisdatastructureintheirwork.B-treesareusedinHFSandReiser4filesystemstoallowforquickaccesstoanyblockinafile.Onaverage,spaceusageisintheorderofO(n).Insert,search,anddeleteoperationsareintheorderofO(logn).

T-treeTheT-treeisabalanceddatastructurethathasboththeindexandactualdatainmemory.Theyareusedinin-memorydatabases.Treferstotheshapeofthenode.Eachnodeconsistsofpointerstotheparentnodeandtheleftandrightchildnodes.Eachnodeinthetreenodewillhaveanorderedarrayofdatapointersandextracontroldata.T-treeshavesimilarperformancebenefitstoin-memorytreestructures.AT-treeisimplementedontopofaself-balancingbinarysearchtree.Thisdatastructureisgoodfororderedscanningofdata.Itsupportsvariousdegreesofisolation.

TablesAswealreadyknow,tablesareusedindatamanagementandotherareas. Atablehasanameandaheaderwiththecolumnnames. Let'stakealookatthedifferentclassesintablessuchasthe Tableclass,theRowclass,theColumnclass,andthePrintTablemethodinthefollowingsections.Forthissection,pleaserefertothe table.gofile.

TheTableclassATableclasshasanarrayofrowsandcolumnnames.Thetable'sNameisastring propertyinthestruct class,asshownhere:

//TableClasstypeTablestruct{Rows[]RowNamestringColumnNames[]string}

TheRowclassTheRowclasshasanarrayofcolumnsandan Id integer,asshowninthefollowingcode.TheIdinstanceisauniqueidentifierforarow:

//RowClasstypeRowstruct{Columns[]ColumnIdint}

TheColumnclassAColumnclasshasanIdinteger andaValue string that'sidentifiedbyauniqueidentifier,aspresentedinthefollowingcodesnippet:

//ColumnClasstypeColumnstruct{IdintValuestring}

TheprintTablemethod

Inthefollowingcodesnippet,theprintTablemethodprintstherowsandcolumnsofatable.Rowsaretraversed,andthenforeveryrowthecolumnsareprinted:

//printTablefuncprintTable(tableTable){varrows[]Row=table.Rowsfmt.Println(table.Name)for_,row:=rangerows{varcolumns[]Column=row.Columnsfori,column:=rangecolumns{fmt.Println(table.ColumnNames[i],column.Id,column.Value);}}}

Themainmethod

Inthismainmethod,wewillinstantiate theclassessuchasTable,Row,and Column,whichwejusttookalookat.Themainmethodcreatesatableandsetsthenameandcolumnnames.Columnsarecreatedwithvalues.Thecolumnsaresetontherowsaftertherowsarecreated. ThetableisprintedbyinvokingtheprintTablemethod,asshownhere:

//mainmethodfuncmain(){vartableTable=Table{}table.Name="Customer"table.ColumnNames=[]string{"Id","Name","SSN"}varrows[]Row=make([]Row,2)rows[0]=Row{}varcolumns1[]Column=make([]Column,3)columns1[0]=Column{1,"323"}columns1[1]=Column{1,"JohnSmith"}columns1[2]=Column{1,"3453223"}rows[0].Columns=columns1rows[1]=Row{}varcolumns2[]Column=make([]Column,3)columns2[0]=Column{2,"223"}columns2[1]=Column{2,"CurranSmith"}columns2[2]=Column{2,"3223211"}rows[1].Columns=columns2table.Rows=rowsfmt.Println(table)printTable(table)}

Runthefollowingcommandtoexecutethetable.gofile:goruntable.go

Theoutputisasfollows:

Thenextsectiontalksaboutthesymboltabledatastructure.

SymboltablesAsymboltableispresentinmemoryduringtheprogramtranslationprocess.Itcanbepresentinprogrambinaries.Asymboltablecontainsthesymbol'sname,location,andaddress.InGo,thegosympackage implementsaccesstotheGosymbolandlinenumbertables.GobinariesgeneratedbytheGCcompilershavethesymbolandlinenumbertables.Alinetableisadatastructurethatmapsprogramcounterstolinenumbers.

ContainersThecontainerspackageprovidesaccesstotheheap,list,andringfunctionalitiesinGo.Containersareusedinsocialnetworks,knowledgegraphs,andotherareas.Containersarelists,maps,slices,channels,heaps,queues,andtreaps. ListswereintroducedinChapter1,DataStructuresandAlgorithms.Mapsandslicesarebuilt-incontainersinGo.ChannelsinGoarecalledqueues.Aheapisatreedatastructure.Thisdatastructuresatisfiestheheapproperty.AqueueismodeledasaheapinChapter3,LinearDataStructures.Atreapisamixofatreeandaheap.Itisabinarytreewithkeysandvaluesandaheapthatmaintainspriorities.Aringiscalledacircularlinkedlistandispresentedinthenextsection. Forthissection,pleaserefertothecircular_list.gofile.

CircularlinkedlistAcircularlinkedlistisadatastructureinwhichthelastnodeisfollowedbythefirstnode.Thecontainer/ringstructuresareusedtomodelcircularlinkedlists.Anexampleimplementationofacircularlinkedlistisshownasfollows:

packagemainimport("container/ring""fmt")funcmain(){varintegers[]intintegers=[]int{1,3,5,7}varcircular_list*ring.Ringcircular_list=ring.New(len(integers))variintfori=0;i<circular_list.Len();i++{circular_list.Value=integers[i]circular_list=circular_list.Next()}

Thering.Newmethodwiththelennasaparametercreatesacircularlistoflengthn.Thecircularlinkedlistisinitializedwithanintegerarraybymovingthrough circular_listwiththeNextmethod.TheDomethodofring.Ringclasstakestheelementasaninterface,andtheelementisprintedasfollows:

circular_list.Do(func(elementinterface{}){fmt.Print(element,",")})fmt.Println()

ThereverseofthecircularlististraversedusingthePrevmethod,andthevalueisprintedinthefollowingcode:

//reverseofthecircularlistfori=0;i<circular_list.Len();i++{fmt.Print(circular_list.Value,",")circular_list=circular_list.Prev()}fmt.Println()

Inthefollowingcodesnippet,thecircularlistismovedtwoelementsforwardusingtheMovemethod,andthevalueisprinted:

//movetwoelementsforwardinthecircularlistcircular_list=circular_list.Move(2)circular_list.Do(func(elementinterface{}){fmt.Print(element,",")})

})

fmt.Println()}

Runthefollowingcommandtoexecutethe circular_list.gofile:goruncircular_list.go

Theoutputisasfollows:

Thenextsectiontalksaboutthehashfunctiondatastructure.

ThehashfunctionsHashfunctionsareusedincryptographyandotherareas.Thesedatastructuresarepresentedwithcodeexamplesrelatedtocryptography.Therearetwowaystoimplementahash functioninGo:withcrc32orsha256.Marshaling(changingthestringtoanencodedform)savestheinternalstate,whichisusedforotherpurposeslater.ABinaryMarshaler (convertingthestringintobinaryform)exampleisexplainedinthissection:

//mainpackagehasexamplesshown//inHands-OnDataStructuresandalgorithmswithGobookpackagemain//importingbytes,crpto/sha256,encoding,fmtandlogpackageimport("bytes""crypto/sha256""encoding""fmt""log""hash")

Themainmethodcreatesabinarymarshaledhashoftwoexamplestrings.Thehashesofthetwostringsareprinted.Thesumofthefirsthashiscomparedwiththesecondhashusingtheequalsmethod onbytes.Thisisshowninthefollowingcode:

//mainmethodfuncmain(){const(example1="thisisaexample"example2="secondexample")varfirstHashhash.HashfirstHash=sha256.New()firstHash.Write([]byte(example1))varmarshalerencoding.BinaryMarshalervarokboolmarshaler,ok=firstHash.(encoding.BinaryMarshaler)if!ok{log.Fatal("firstHashisnotgeneratedbyencoding.BinaryMarshaler")}vardata[]bytevarerrerrordata,err=marshaler.MarshalBinary()iferr!=nil{log.Fatal("failuretocreatefirstHash:",err)}varsecondHashhash.HashsecondHash=sha256.New()varunmarshalerencoding.BinaryUnmarshalerunmarshaler,ok=secondHash.(encoding.BinaryUnmarshaler)

unmarshaler,ok=secondHash.(encoding.BinaryUnmarshaler)

if!ok{log.Fatal("secondHashisnotgeneratedbyencoding.BinaryUnmarshaler")}iferr:=unmarshaler.UnmarshalBinary(data);err!=nil{log.Fatal("failuretocreatehash:",err)}firstHash.Write([]byte(example2))secondHash.Write([]byte(example2))fmt.Printf("%x\n",firstHash.Sum(nil))fmt.Println(bytes.Equal(firstHash.Sum(nil),secondHash.Sum(nil)))}

Runthefollowingcommandtoexecutethehash.gofile:gorunhash.go

Theoutputisasfollows:

SummaryThischaptercoveredtrees,binarysearchtrees,andAVLtrees.Treap,B-trees,andB+treeswereexplainedbriefly.Operationssuchasinsertion,deletion,andupdatingelementsintreeswereshownwithvariouscodeexamples.Tables,containers,andhashfunctionswerepresentedinthelastsection.Thecomplexityintimeandspaceforoperationssuchasinsertion,deletion,andsearchwereexplainedineachsection.Inthenextchapter,homogeneousdatastructuressuchastwo-dimensionalandmulti-dimensionalarrayswillbecovered.

Questions1. Canyougiveanexamplewhereyoucanuseabinarysearchtree?2. Whichmethodisusedtosearchforanelementinabinarysearchtree?3. WhichtechniquesareusedtoadjustthebalanceinanAVLtree?4. Whatisasymboltable?

1. Whichclassandmethodarecalledtogenerateabinarymarshaledhashonthehashclass?

2. WhichcontainerinGoisusedtomodelacircularlinkedlist?3. HowdoyoucreateaJSON(indented)fromatreestructure?Whichclassandmethodareused?

4. Howdoyoucomparethesumofhashes?5. WhatisthebalancefactorinanAVLtree?6. Howdoyouidentifyarowandcolumninatable?

Furtherreading

Thefollowingbooksarerecommendedifyouwanttoknowmoreabouttrees,binarysearchtrees,andAVLtrees:

DesignPatterns, byErichGamma,RichardHelm,RalphJohnson,andJohnVlissidesIntroductiontoAlgorithms –ThirdEdition,byThomasH.Cormen,CharlesE.Leiserson,RonaldL.Rivest,andCliffordSteinDatastructuresandAlgorithms:AnEasyIntroduction,by RudolphRussell

HomogeneousDataStructuresHomogeneousdatastructurescontainsimilartypesofdata,suchasintegersordoublevalues.Homogeneousdatastructuresareusedinmatrices,aswellastensorandvectormathematics. Tensorsaremathematicalstructuresforscalarsandvectors. Afirst-ranktensorisavector.Avectorconsistsofaroworacolumn.Atensorwithzerorankisascalar. Amatrixisatwo-dimensionalclusterofnumbers. Theyareallusedinscientificanalysis.Tensorsareusedinmaterialscience.Theyareusedinmathematics,physics,mechanics,electrodynamics,andgeneralrelativity.Machinelearningsolutionsutilizeatensordatastructure.Atensorhaspropertiessuchasposition,shape,andastaticsize.Thischaptercoversthefollowinghomogeneousdatastructures:

Two-dimensional arraysMulti-dimensionalarrays

Thefollowingscenariosareshowntodemonstratetheusageoftwo-dimensionalandmulti-dimensionalarrays:

MatrixrepresentationMultiplicationAdditionSubtractionDeterminantcalculationInversionTransposition

TechnicalrequirementsInstallGoVersion1.10from https://golang.org/doc/install foryourOS.TheGitHubURLforthecodeinthischapterisasfollows: https://github.com/PacktPublishing/Learn-Data-Structures-and-Algorithms-with-Golang/tree/master/Chapter05.

Two-dimensionalarraysTwo-dimensionalarrayswerepresentedbrieflyinChapter2,GettingStartedwithGoforDataStructuresandAlgorithms.Torecap,fordynamicallocation,weusesliceofslices,whichisatwo-dimensionalarray.Atwo-dimensionalarray,is alistof single-dimensionalarrays.Everyelementinatwo-dimensionalarrayarr,isidentifiedasarr[i][j],wherearristhenameofthearrayandiandjrepresentrowsandcolumns,andtheirvaluesrangingfrom0tomand0ton,respectively.Traversingatwo-dimensionalarrayisofO(m*n)complexity.Thefollowingcodeshowshowtoinitializeanarray:

vararr=[4][5]int{

{4,5,7,8,9},

{1,2,4,5,6},

{9,10,11,12,14},

{3,5,6,8,9}}

Anelementinatwo-dimensionalarrayisaccessedwitharowindexandcolumnindex.Inthefollowingexample,thearray'svalueinrow2andcolumn3isretrievedasanintegervalue:

varvalueint=arr[2][3]

Arrayscanstoreasequentialcollectionofdataelementsofthesametype.Homogeneousdatastructurearraysconsistofcontiguousmemoryaddresslocations.Two-dimensionalmatricesaremodeledastwo-dimensionalarrays.Ascalarisanelementofafieldthatdefinesavectorspace.Amatrixcanbemultipliedbyascalar.Youcandivideamatrixbyanynon-zerorealnumber.Theorderofamatrixisthenumberofrows, m,bythenumberofcolumns, n.Amatrixwithrowsmandcolumnsnisreferredtoasanmxnmatrix.Thereare multipletypes of matrices,suchasarowmatrix,

nmatrix.Thereare multipletypes of matrices,suchasarowmatrix,

columnmatrix,triangularmatrix,nullmatrix,andzeromatrix; let'sdiscusstheminthefollowingsections.

RowmatrixArowmatrixisa1xmmatrixconsistingofasinglerowofmelements,asshownhere:

varmatrix=[1][3]int{{1,2,3}}

Runthefollowingcommandtoexecutetherow_matrix.gofile:gorunrow_matrix.go

Theoutputisasfollows:

Thenextsectiontalksaboutthecolumnmatrixdatastructure.

ColumnmatrixAcolumnmatrixisanmx1matrixthathasasinglecolumnofmelements.Thefollowingcodesnippetshowshowtocreateacolumnmatrix:

varmatrix=[4][1]int{{1},{2},{3},{4}}

Runthefollowingcommandtoexecutethecolumn_matrix.gofile:goruncolumn_matrix.go

Theoutputisasfollows:

Thenextsectiontalksaboutthelowertriangularmatrixdatastructure.

LowertriangularmatrixAlowertriangularmatrixconsistsofelementsthathaveavalueofzeroabovethemaindiagonal.Thefollowingcodesnippetshowshowto createalowertriangularmatrix:

varmatrix=[3][3]int{{1,0,0},{1,1,0},{2,1,1}}

Runthefollowingcommandtoexecutethelower_triangular.gofile:gorunlower_triangular.go

Theoutputisasfollows:

Thenextsectiontalksabouttheuppertriangularmatrixdatastructure.

UppertriangularmatrixAnuppertriangularmatrixconsistsofelementswithavalueofzerobelowthemaindiagonal.Thefollowingcodecreatesanuppertriangularmatrix:

varmatrix=[3][3]int{{1,2,3},{0,1,4},{0,0,1}}

Runthefollowingcommandtoexecutetheupper_triangular.gofile:gorunupper_triangular.go

Theoutputisasfollows:

Thenextsectiontalksaboutthe nullmatrixdatastructure.

NullmatrixAnullorazeromatrixisamatrixentirelyconsistingofzerovalues,asshowninthefollowingcodesnippet:

varmatrix=[3][3]int{{0,0,0},{0,0,0},{0,0,0}}

Runthefollowingcommandtoexecutethenull_matrix.gofile:gorunnull_matrix.go

Theoutputisasfollows:

Thenextsectiontalksabouttheidentitymatrixdatastructure.

IdentitymatrixAnidentitymatrixisaunitmatrixwithonesareonthemaindiagonalandzerosareelsewhere. Thefollowingcodesnippetcreatesanidentitymatrix:

///mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingfmtpackage

import(

"fmt")//identitymethod

funcIdentity(orderint)[][]float64{

varmatrix[][]float64matrix=make([][]float64,order)

variint

fori=0;i<order;i++{

vartemp[]float64temp=make([]

float64,order)temp[i]=1matrix[i]=temp

}

returnmatrix

}

//mainmethod

funcmain(){fmt.Println(Identity(4))

}

Runthefollowingcommandtoexecutetheprecedingcodesnippet:gorunidentity_matrix.go

Theoutputisasfollows:

Thenextsectiontalksaboutthesymmetricmatrixdatastructure.

SymmetricmatrixAsymmetricmatrixisamatrixwhosetransposeisequaltoitself.Symmetricmatricesincludeothertypesofmatricessuchasantimetric,centrosymmetric,circulant,covariance,coxeter,hankel,hilbert,persymmetric,skew-symmetric,andtoeplitzmatrices.Anegativematrixisamatrixinwhicheachelementisanegativenumber. 

Basic2DmatrixoperationsInthissection,wewilllookatthebasicoperationsonthetwo-dimensionalmatrix.Let'sstartwithinitializingthematrices.matrix1andmatrix2areinitializedinthefollowingcodesnippet:

varmatrix1=[2][2]int{

{4,5},

{1,2}

}

varmatrix2=[2][2]int{

{6,7},

{3,4}

}

Theadd,subtract,multiply,transpose,andinversionoperations arepresentedinthenextfewsections. Forthissection,pleaserefertothe binary_search_tree.go file.

Theaddmethod

Theaddmethodaddstheelementsoftwo2x2matrices.Thefollowingcodereturnsthecreatedmatrixbyaddingthetwomatrices:

//addmethod

funcadd(matrix1[2][2]int,matrix2[2][2]int)[2][2]int{

varmint

varlint

varsum[2][2]int

forl=0;l<2;l++{

form=0;m<2;m++{

sum[l][m]=matrix1[l][m]+matrix2[l][m]

}

}

returnsum

}

Thesumbetweenthetwomatricesistheresultofcallingthe add method.Theparametersthatarepassedarethematricestobeadded,asshownhere:

varsum[2][2]int

sum=add(matrix1,matrix2)

Theexampleoutputoftheaddmethodisasfollows.Addingmatrix1andmatrix2givesasummatrix:

Thesubtractmethod

Thesubtractmethodsubtractstheelementsoftwo2x2matrices.Thesubtractmethodinthefollowingsnippetsubtractstheelementsofmatrix1andmatrix2.Thismethodreturnstheresultingmatrixaftersubtraction:

//subtractmethod

funcsubtract(matrix1[2][2]int,matrix2[2][2]int)[2][2]int{

varmint

varlint

vardifference[2][2]int

forl=0;l<2;l++{

form=0;m<2;m++{

difference[l][m]=matrix1[l][m]-matrix2[l][m]

}

}

returndifference

}

Thedifferencebetweentwomatricesistheresultofcallingthesubtractmethod.Theparametersthatare passedarethematricestobesubtracted,asshownhere:

vardifference[2][2]int

difference=subtract(matrix1,matrix2)

Theexampleoutputofthesubtractmethodisasfollows:

Themultiplymethod

Themultiplymethodmultipliestheelementsoftwo2x2matrices.Themultiplicationoftwomatrices,matrix1andmatrix2,isshowninthefollowingsnippet.Thematrixthat's generated afterthemultiplicationisreturnedbythemultiplymethod:

//multiplymethodfuncmultiply(matrix1[2][2]int,matrix2[2][2]int)[2][2]int{varmintvarlintvarnintvarproduct[2][2]intforl=0;l<2;l++{form=0;m<2;m++{varproductSumint=0forn=0;n<2;n++{productSum=productSum+matrix1[l][n]*matrix2[n][m]}product[l][m]=productSum;}}returnproduct}

Theproductoftwomatricesiscalculatedusingthemultiplymethodinthefollowingcodesnippet,whichtakesthetwomatricesasparameters:

varproduct[2][2]int

product=multiply(matrix1,matrix2)

Theexampleoutputofthemultiplymethodisasfollows.Theproductofmatrix1andmatrix2istheproductmatrix:

Thetransposemethod

Thetransposeofamatrixisachievedusingthetransposemethod.Thismethodtakesthematrixasaparameterandreturnsthetransposedmatrix:

//transposemethod

functranspose(matrix1[2][2]int)[2][2]int{varmintvarlintvartransMatrix[2][2]intforl=0;l<2;l++{form=0;m<2;m++{

transMatrix[l][m]=matrix1[m][l]

}}returntransMatrix}

Thedeterminantmethod

Thedeterminantmethodcalculatesthedeterminantofthematrix.Thedeterminantmethodinthefollowingcodesnippetcalculatesthedeterminantvalueofamatrix.Themethodtakesthematrixandreturnsafloat32value,whichisthedeterminantofthematrix:

//determinantmethodfuncdeterminant(matrix1[2][2]int)float32{

varmint

varlint

vardetfloat32

det=det+((matrix1[0][0]*matrix1[1][1])-(matrix1[0][1]*matrix1[1][0]));

returndet

}

Theinversemethod

Theinversemethodreturnstheinverseofthematrix,whichispassedasaparameter.Thisisshowninthefollowingsnippet:

//inversemethod

funcinverse(matrix[2][2]int)[][]float64{

vardetfloat64

det=determinant(matrix)

varinvmatrixfloat64

invmatrix[0][0]=matrix[1][1]/det

invmatrix[0][1]=-1*matrix[0][1]/det

invmatrix[1][0]=-1*matrix[1][0]/det

invmatrix[1][1]=matrix[0][0]/det

returninvmatrix

}

Runthefollowingcommandtoexecutethetwodmatrix.gofile:goruntwodmatrix.go

Theoutputisasfollows:

Thenextsectiontalksaboutthezig-zagmatrixdatastructure.

Zig-zagmatrixAzig-zagmatrixisasquarearrangementofn x nintegers.Theintegersarearrangedonanti-diagonalsinsequentiallyincreasingorder.Thefollowingcodeexplainshowtocreateazig-zagmatrixandalsohowtotraverseit.The PrintZigZagmethodcreatesthematrixinazig-zagfashionwiththeelementsinasequentiallyincreasingorder.Themethodtakestheintegernasaparameterandreturnstheintegerarray,whichisthezig-zagmatrix:

///mainpackagehasexamplesshown

//inGoDataStructuresandalgorithmsbook

packagemain

//importingfmtpackage

import(

"fmt"

)

//printsthematrixinzig-zagfashion

funcPrintZigZag(nint)[]int{

varzigzag[]int

zigzag=make([]int,n*n)

variint

i=0

varmint

m=n*2

varpint

forp=1;p<=m;p++{

varxint

x=p-n

ifx<0{

x=0

}

varyint

y=p-1

ify>n-1{

y=n-1

}

varjint

j=m-p

ifj>p{

j=p

}

varkint

fork=0;k<j;k++{

ifp&1==0{

zigzag[(x+k)*n+y-k]=i

}else{

zigzag[(y-k)*n+x+k]=i

}

}

i++

}

}

returnzigzag

}

ThemainmethodinvokesthePrintZigZagmethod,whichtakestheparameternandprintsthematrixfirst fromlefttoright,thenfromrighttoleftforthesecondlevel,andsoon.Thenumberofintegersis5andthefieldwidthis2:

//mainmethod

funcmain(){

varnintn=5

varlengthint

length=2

variint

varsketchint

varsketchint

fori,sketch=rangePrintZigZag(n){

fmt.Printf("%*d",length,sketch)

ifi%n==n-1{

fmt.Println("")

}

}

}

Runthefollowingcommandtoexecutethezigzagmatrix.gofile:gorunzigzagmatrix.go

Theoutputisasfollows:

Thenextsectiontalksaboutthe spiralmatrixdatastructure.

SpiralmatrixAspiralmatrixisanarrangementofn x nintegersinwhichintegersarearrangedspirallyinsequentiallyincreasingorder.Aspiralmatrixisanoldtoyalgorithm.Thespiralorderismaintainedusingfourloops,one foreachcornerofthematrix.The PrintSpiralmethodinthefollowingcodesnippetcreatesamatrixwithelements arrangedspirallyinincreasingorder.Themethodtakesaparameter,n,andreturnsanintegerarray:

///mainpackagehasexamplesshown

//inGoDataStructuresandalgorithmsbook

packagemain

//importingfmtpackage

import(

"fmt"

)

//PrintSpiralmethodfuncPrintSpiral(nint)[]int{

varleftintvartopintvarrightintvarbottomint

left=0top=0right=n-1bottom=n-1varsizeintsize=n*nvars[]ints=make([]int,size)

variinti=0forleft<right{

varcintforc=left;c<=right;c++{s[top*n+c]=ii++}top++

varrintforr=top;r<=bottom;r++{s[r*n+right]=ii++}right--iftop==bottom{break}

forc=right;c>=left;c--{s[bottom*n+c]=ii++}bottom--

forr=bottom;r>=top;r--{s[r*n+left]=ii++}left++}

s[top*n+left]=i

returns}

Inthefollowingcodesnippet, themainmethodinvokesthePrintSpiralmethod,whichtakestheintegernandprintstheintegervaluesofthematrix spirally.ThevaluesreturnedfromthePrintSpiralmethodareprintedasfieldswithawidthof2:

funcmain(){varnintn=5varlengthintlength=2

length=2

variintvarsketchintfori,sketch=rangePrintSpiral(n){fmt.Printf("%*d",length,sketch)ifi%n==n-1{fmt.Println("")}}}

Runthefollowingcommandtoexecutethespiralmatrix.gofile:gorunspiralmatrix.go

Theoutputisasfollows:

ThenextsectiontalksabouttheBooleanmatrixdatastructure.

BooleanmatrixABooleanmatrixisamatrix thatconsistsofelementsinthemth rowandthenth columnwithavalueof1. AmatrixcanbemodifiedtobeaBooleanmatrixbymakingthevaluesinthe mth rowandthe nth columnequalto1.Inthefollowingcode,theBooleanmatrixtransformationandprintmethodsareshownindetail.ThechangeMatrixmethodtransformstheinputmatrixintoaBooleanmatrixbychangingtherowandcolumnvaluesfrom0to1ifthecellvalueis1.Themethodtakestheinputmatrixastheparameterandreturnsthechangedmatrix,asshowninthefollowingcode:

///mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingfmtpackageimport("fmt")//changeMatrixmethodfuncchangeMatrix(matrix[3][3]int)[3][3]int{variintvarjintvarRows[3]intvarColumns[3]int

varmatrixChanged[3][3]int

fori=0;i<3;i++{forj=0;j<3;j++{ifmatrix[i][j]==1{Rows[i]=1Columns[j]=1}

}}

fori=0;i<3;i++{forj=0;j<3;j++{ifRows[i]==1||Columns[j]==1{matrixChanged[i][j]=1}

}

}

}

returnmatrixChanged

}

Theexampleoutputofthechangematrixmethodisshownthefollowingscreenshot.Theelementswith1intheroworcolumnarecheckedandtherowelementsareupdatedto1:

Let'stakealookattheprintMatrixmethodandthemainmethod.

TheprintMatrix method

Inthefollowingcodesnippet, the printMatrixmethodtakestheinputmatrixandprintsthematrixvaluesbyrowandtraversesthecolumnsforeveryrow:

//printMatrixmethodfuncprintMatrix(matrix[3][3]int){variintvarjint//varkintfori=0;i<3;i++{

forj=0;j<3;j++{

fmt.Printf("%d",matrix[i][j])

}fmt.Printf("\n")}

}

Themainmethod

ThemainmethodinthefollowingcodesnippetinvokesthechangeMatrix methodafterinitializingthematrix.Thechanged matrixisprintedaftertheinvocationofthechangeMatrixmethod:

//mainmethodfuncmain(){

varmatrix=[3][3]int{{1,0,0},{0,0,0},{0,0,0}}

printMatrix(matrix)

matrix=changeMatrix(matrix)

printMatrix(matrix)

}

Runthefollowingcommandtoexecutetheboolean_matrix.gofile:gorunboolean_matrix.go

Theoutputisasfollows:

Thenextsectiontalksaboutmulti-dimensionalarrays.

Multi-dimensionalarraysAnarrayisahomogeneouscollectionofdataelements.Anarray'sindexesrangefromindex0toindexm-1,wheremisthefixedlengthofthearray.Anarraywithmultipledimensionsisanarrayofanarray.Thefollowingcodeinitializesamulti-dimensionalarray. Athree-dimensionalarrayisprinted:

///mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingfmtpackageimport("fmt""math/rand")//mainmethodfuncmain(){

varthreedarray[2][2][2]int

variint

varjint

varkint

fori=0;i<2;i++{

forj=0;j<2;j++{

fork=0;k<2;k++{

threedarray[i][j][k]=rand.Intn(3)}}}

fmt.Println(threedarray)}

Runthefollowingcommandtoexecutetheprecedingcodesnippet:gorunmultidarray.go

Theoutputisasfollows:

Thenextsectiontalksabouttensordatastructures.

TensorsAtensorisamulti-dimensionalarrayofcomponentsthatarespatialcoordinates.Tensorsareusedextensively inphysicsandbiologicalstudiesintopicssuchaselectromagnetismanddiffusiontensorimaging.WilliamRowanHamiltonwasthefirsttocomeupwiththetermtensor.Tensorsplayabasicroleinabstractalgebraandalgebraictopology.Thetensororderisthesumoftheorderofitsarguments,plustheorderoftheresulttensor.Forexample,aninertiamatrixisasecond-ordertensor.Spinorsarealsomulti-dimensionalarrays,butthevaluesoftheirelementschangeviacoordinatetransformations.Theinitializationofatensorisshownhere.Thearrayisinitializedwithintegervaluesrangingfrom0to3:

vararray[3][3][3]intvariintvarjintvarkintfori=0;i<3;i++{forj=0;j<3;j++{fork=0;k<3;k++{

array[i][j][k]=rand.Intn(3)}}}

Unfoldingatensorisdonealongthefirstdimension.Rearrangingthetensormode'snvectorsisreferredtoasmoden-unfoldingofatensor.0-modeunfoldingofatensorarrayisshownhere:

forj=0;j<3;j++{fork=0;k<3;k++{fmt.Printf("%d",array[0][j][k])}fmt.Printf("\n")}

1-modeunfoldingofatensorarrayisshownhere.Thearray'sfirstdimensionindexissetto1:

forj=0;j<3;j++{fork=0;k<3;k++{fmt.Printf("%d",array[1][j][k])}fmt.Printf("\n")

fmt.Printf("\n")

}

The2-modeunfoldingofatensorarrayisshownhere.Thearray'sfirstdimensionrowindexissetto2:

forj=0;j<3;j++{fork=0;k<3;k++{fmt.Printf("%d",array[2][j][k])}fmt.Printf("\n")}

Runthefollowingcommandtoexecutethetensor.gofile:goruntensor.go

Theoutputisasfollows:

SummaryThischaptercoveredhomogeneousdatastructuressuchastwo-dimensionalarraysandmulti-dimensionalarrays.Matrixoperationssuchassum,subtraction,multiplication,inverse, anddeterminanthavebeenexplainedwithcodeexamples.Spiralmatrices,zig-zagmatrices,andBooleanmatriceshavebeenexplainedusingtwo-dimensionalarrays.Tensorsandoperationssuchasfoldingwerealsocovered.Inthenextchapter,heterogeneousdatastructuressuchaslinkedlists,orderedlists,andunorderedlistswillbecovered.

Questions1. Whatis2-modeunfoldingofatensorarray?2. Writeatwo-dimensionalarrayofstringsandinitializeit.Printthestrings.3. Giveanexampleofamulti-dimensionalarrayandtraversethroughit.4. Fora3x3matrix,writecodethatcalculatesthedeterminantofthematrix.

5. Whatisatransposeofa3x3matrix?6. Whatisazig-zagmatrix?7. Writecodewithanexampleofaspiralmatrix.8. Whichdimensionistypicallyunfoldedfortensorarrays?9. HowdoyoudefineaBooleanmatrix?10. Choosetwo3x3matricesandfindtheproductofthematrices.

Furtherreading

Thefollowingbooksarerecommendedifyouwanttolearnmoreaboutarrays,matrices,andtensors:

AdvancedDataStructures,by PeterBrassDynamicDataStructures:Lists,Stacks,Queues,andTrees, byBogdanPatrut,andTiberiuSocaciuDatastructuresandAlgorithms:AnEasyIntroduction,by RudolphRussell

HeterogeneousDataStructuresHeterogeneousdatastructuresaredatastructuresthatcontaindiversetypesofdata,suchasintegers,doubles,andfloats.Linkedlistsandorderedlistsaregoodexamplesofthesedatastructures.Theyareusedformemorymanagement.Alinkedlistisachainofelementsthatareassociatedtogetherbymeansofpointers.Eachelement'spointerlinkstothefollowingitem,whichconnectsthechaintogether.Linkedlistsdon'thavetotakeupablockofmemory.Thememorythattheyutilizecanbeallocateddynamically.Itcomprisesaprogressionofnodes,whicharethecomponentsofthelist.OrderedlistsandunorderedlistsfromHTMLareshowntodemonstratetheusageoflistsandstoragemanagement.Wewillcoverlinkedlists,orderedlists,andunorderedlistsinthischapterandshowtheimplementationoftheirmethodswithappropriateexamples.Thischaptercoversthefollowingheterogeneousdatastructures:

LinkedlistsOrderedlistsUnorderedlists

WecoveredsinglylinkedlistsanddoublylinkedlistswithcodeexamplesinChapter3,LinearDataStructures.Circular-linkedlistswerecoveredinChapter4,Non-LinearDataStructures.

TechnicalrequirementsInstallGoVersion1.10foryourOSfromthefollowinglink:https://golang.org/doc/install.TheGitHubURLforthecodeinthischapterisasfollows:https://github.com/PacktPublishing/Learn-Data-Structures-and-Algorithms-with-Golang/tree/master/Chapter06.

LinkedlistsAlinkedlistisalinearcollectionofelementswithinformation.Thelinkedlistshrinksorexpandsbasedonwhetherthecomponentsaretobeincludedorremoved.Thislistcanbesmallorenormous,yet,regardlessofthesize,theelementsthatmakeituparestraightforward.LinkedlistswerecoveredinChapter3,LinearDataStructures.Theyconsumemorememorythanarrays.Reversetraversingisaproblemforsinglylinkedlistsbecauseasinglylinkedlistpointstothenextnodeforward.Thenextsectionexplainshowtoreverseasinglylinkedlistwithacodeexample.Singly,doubly,andcircular-linkedlistswillbecoveredinthischapter.

SinglylinkedlistsAsinglylinkedlistisadynamicdatastructureinwhichadditionandremovaloperationsareeasy;thisisbecauseit'sadynamicdatastructureandnotfixed.Stackandqueuedatastructuresareimplementedwithlinkedlists.Morememoryisconsumedwhenelementsaredynamicallyaddedbecausedynamicdatastructuresaren'tfixed.Randomretrievalisnotpossiblewithasinglylinkedlistbecauseyouwillneedtotraversethenodesforapositionednode.Insertionintoasinglylinkedlistcanbeatthebeginningorendofthelist,andafteraspecifiednode.Deletioncanhappenatthebeginningorendofthelistandafteraspecifiednode.Reversingasinglylinkedlistisshowninthissection.Themethodsthatareexplainedinthissectionareapartofthelinked_list.gofilethat'sprovidedinthecodebundle.TheNodeclassisdefinedinthissnippetwithanodepointer,nextNode,andaruneproperty:

//mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingfmtpackageimport("fmt")

//NodestructtypeNodestruct{nextNode*Nodepropertyrune}

Themethodsofsinglylinkedlistsarediscussedinthefollowingsections.

TheCreateLinkedListmethod

TheCreateLinkedListmethodcreatesalinkedlistofrunesfromatoz://createListmethodfuncCreateLinkedList()*Node{varheadNode*NodeheadNode=&Node{nil,'a'}varcurrNode*NodecurrNode=headNodevarirunefori='b';i<='z';i++{varnode*Nodenode=&Node{nil,i}currNode.nextNode=nodecurrNode=node}returnheadNode}

TheexampleoutputfortheCreateLinkedListmethodisshownasfollows.TheheadNodeiscreatedwithavalueof97.Thelinkedlistiscreatedwithnodesstartingfromatoz:

TheReverseLinkedListmethod

TheReverseLinkedListfunctiontakesanodepointer,nodeList,andreturnsanodepointertoareversedlinkedlist.Thefollowingcodesnippetshowshowthelinkedlistisreversed:

//ReverseListmethodfuncReverseLinkedList(nodeList*Node)*Node{varcurrNode*NodecurrNode=nodeListvartopNode*Node=nilfor{ifcurrNode==nil{break}vartempNode*NodetempNode=currNode.nextNodecurrNode.nextNode=topNodetopNode=currNodecurrNode=tempNode}returntopNode}

Theexampleoutputforthereverselinkedlistmethodisasfollows.Themethodtakestheparameterofalinkedstringstartingfromatoz.Thereversedlistisfromztoanodes:

Themainmethod

Themainmethodcreatesthelinkedlist,andprintsthelinkedlistandthereversedlistinstringformat:

//mainmethodfuncmain(){varlinkedList=CreateLinkedList()StringifyList(linkedList)StringifyList(ReverseLinkedList(linkedList))}

Runthefollowingcommandtoexecutethelinked_list.gofile:gorunlinked_list.go

Thisistheoutput:

Thenextsectiontalksaboutthedoublylinkedlistdatastructure.

DoublylinkedlistsAdoublylinkedlistisadatastructurethatconsistsofnodesthathavelinkstothepreviousandthenextnodes.DoublylinkedlistswerepresentedwithcodeexamplesinChapter3,LinearDataStructures.ListsinGoareimplementedasdoublylinkedlists.Theelements14and1arepushedbackwardandforward,respectively.Theelements6and5areinsertedbeforeandafter.Thedoublylinkedlistisiteratedandtheelementsareprinted.Thecodeinthissectionshowshowlistscanbeused:

//mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingfmtandlistpackageimport("container/list""fmt")

//mainmethodfuncmain(){varlinkedList*list.ListlinkedList=list.New()varelement*list.Elementelement=linkedList.PushBack(14)varfrontElement*list.ElementfrontElement=linkedList.PushFront(1)linkedList.InsertBefore(6,element)linkedList.InsertAfter(5,frontElement)

varcurrElement*list.ElementforcurrElement=linkedList.Front();currElement!=nil;currElement=currElement.Next(){fmt.Println(currElement.Value)}}

Runthefollowingcommandtoexecutethedouble_linked_list.gofile:gorundouble_linked_list.go

Thisistheoutput:

Thenextsectiontalksaboutthecircular-linkedlistdatastructure.

Circular-linkedlistsAcircular-linkedlistisacollectionofnodesinwhichthelastnodeisconnectedtothefirstnode.Circular-linkedlistswerebrieflycoveredinChapter4,Non-LinearDataStructures.Circular-linkedlistsareusedtocreateacircularqueue.Inthefollowingsection,acircularqueuestructisdefinedandimplemented.Themethodsthatareexplainedinthissectionarepartofthecircular_queue.gofilegiveninthecodebundle.

TheCircularQueueclassTheCircularQueueclasshassize,head,andlastintegerproperties,aswellasanodesarray.Theclassisdefinedinthefollowingcodesnippet:

//mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingfmtpackageimport("fmt")

//CircularQueuetypeCircularQueuestruct{sizeintnodes[]interface{}headintlastint}

Let'sdiscussthedifferentmethodsoftheCircularQueueclassinthefollowingsections.

TheNewQueuemethod

TheNewQueuemethodcreatesanewinstanceofthecircularqueue.TheNewQueuefunctiontakesthenumparameter,whichisthesizeofthequeue.Thefunctionreturnsthecircularqueueofnodes,asshowninthefollowingcode:

//NewCircularQueuemethodfuncNewQueue(numint)*CircularQueue{varcircularQueueCircularQueuecircularQueue=CircularQueue{size:num+1,head:0,last:0}circularQueue.nodes=make([]interface{},circularQueue.size)return&circularQueue}

TheIsUnUsedmethod

TheIsUnUsedmethodoftheCircularQueueclassinthefollowingsnippetcheckswhetherheadisequaltothelastnodeandreturnstrueifso;otherwise,itreturnsfalse:

//IsUnUsedmethodfunc(circularQueueCircularQueue)IsUnUsed()bool{returncircularQueue.head==circularQueue.last}

TheIsCompletemethod

TheIsCompletefunctionoftheCircularQueueclassreturnstrueiftheheadnode'spositionisthesameasthelastnodeposition+1;otherwise,itreturnsfalse:

//IsCompletemethodfunc(circularQueueCircularQueue)IsComplete()bool{returncircularQueue.head==(circularQueue.last+1)%circularQueue.size}

TheAddmethod

Thismethodaddsthegivenelementtothecircularqueue.Inthefollowingcodesnippet,theAddmethodtakesanelementparameteroftheinterfacetypeandaddstheelementtothecircularqueue:

//Addmethodfunc(circularQueue*CircularQueue)Add(elementinterface{}){ifcircularQueue.IsComplete(){panic("QueueisCompletelyUtilized")}circularQueue.nodes[circularQueue.last]=elementcircularQueue.last=(circularQueue.last+1)%circularQueue.size}

TheexampleoutputfortheAddmethodisasfollows.TheAddmethodtakestheelementwithvalue1andupdatesthequeue:

TheMoveOneStepmethod

TheMoveOnestepmethodmovestheelementonestepforwardinthecircularqueue.TheMoveOneStepmethodtakestheelementparameteroftheinterfacetypeandmovestheheadnodetopositiontwoaftersettingtheelementastheheadnode:

//MoveOneStepmethodfunc(circularQueue*CircularQueue)MoveOneStep()(elementinterface{}){ifcircularQueue.IsUnUsed(){returnnil}element=circularQueue.nodes[circularQueue.head]circularQueue.head=(circularQueue.head+1)%circularQueue.sizereturn}

Themainmethod

Themainmethodcreatesthequeueandaddselementstothecircularqueue:

//mainmethodfuncmain(){varcircularQueue*CircularQueuecircularQueue=NewQueue(5)circularQueue.Add(1)circularQueue.Add(2)circularQueue.Add(3)circularQueue.Add(4)circularQueue.Add(5)fmt.Println(circularQueue.nodes)

}

Runthefollowingcommandtoexecutethecircular_queue.gofile:goruncircular_queue.go

Thisistheoutput:

Inthefollowingsections,orderedlistsandunorderedlistsareexplainedwithcodeexamples.

OrderedlistsListsinGocanbesortedintwoways:

Orderedlist:BycreatingagroupofmethodsfortheslicedatatypeandcallingsortUnorderedlist:Theotherwayistoinvokesort.Slicewithacustomlessfunction

Theonlydifferencebetweenanorderedlistandanunorderedlististhat,inanorderedlist,theorderinwhichtheitemsaredisplayedismandatory.AnorderedlistinHTMLstartswithan<ol>tag.Eachiteminthelistiswrittenin<li>tags.Here'sanexample:

<ol>

<li>Stones</li>

<li>Branches</li>

<li>Smoke</li>

</ol>

AnexampleofanorderedlistusingGolangisshowninthefollowingcodesnippet.TheEmployeeclasshasName,ID,SSN,andAgeproperties:

///mainpackagehasexamplesshown

//inGoDataStructuresandalgorithmsbook

packagemain

//importingfmtandsortpackage

import(

"fmt"

"sort"

)

//classEmployee

typeEmployeestruct{

Namestring

IDstring

SSNint

Ageint

}

Themethodsthatareexplainedinthefollowingsectionsareapartofthelinked_list.gofilethat'sprovidedinthecodebundle.

TheToStringmethod

TheToStringmethodoftheEmployeeclassreturnsastringversionofemployee.Thestringversionconsistsofacomma-separatedName,Age,ID,andSSN.Thisisshowninthefollowingcodesnippet:

//ToStringmethod

func(employeeEmployee)ToString()string{

returnfmt.Sprintf("%s:%d,%s,%d",employee.Name,employee.Age,employee.ID,employee.SSN)

}

TheSortByAgetypeTheSortByAgemethodsortstheelementsconcernedbyAge.TheSortByAgeinterfaceoperatesontheEmployeearray.Thisisshowninthefollowingcodesnippet:

//SortByAgetype

typeSortByAge[]Employee

//SortByAgeinterfacemethods

func(sortIntfSortByAge)Len()int{returnlen(sortIntf)}

func(sortIntfSortByAge)Swap(iint,jint){sortIntf[i],sortIntf[j]=sortIntf[j],sortIntf[i]}

func(sortIntfSortByAge)Less(iint,jint)bool{returnsortIntf[i].Age<sortIntf[j].Age}

Themainmethodinitializestheemployeesarrayandsortsthearraybyage:

funcmain(){

varemployees=[]Employee{

{"Graham","231",235643,31},

{"John","3434",245643,42},

{"Michael","8934",32432,17},

{"Jenny","24334",32444,26},

}

fmt.Println(employees)

sort.Sort(SortByAge(employees))

fmt.Println(employees)

sort.Slice(employees,func(iint,jint)bool{

returnemployees[i].Age>employees[j].Age

})

fmt.Println(employees)

}

Runthefollowingcommandtoexecutethesort_slice.gosnippet:gorunsort_slice.go

Thisistheoutput:

Anorderedlistissortedusingthesortcriteriaasfollows.Thesort_keys.gocodesnippetshowshowthingsaresortedbyvariouscriteria,suchasname,mass,anddistance.TheMassandMilesunitsaredefinedasfloat64:

///mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingfmtandsortpackageimport("fmt""sort")

//MassandMilesTypestypeMassfloat64typeMilesfloat64

ThenextsectiontalksabouttheThingstructdefinition.

TheThingclassAThingclassisdefinedinthefollowingcodewithname,mass,distance,meltingpoint,andfreezingpointproperties:

//ThingclasstypeThingstruct{namestringmassMassdistanceMilesmeltingpointintfreezingpointint}

ThenextsectiontalksabouttheByFactorfunctiontype.

TheByFactorfunctiontypeByFactorisatypeoflessfunction.ThefollowingcodesnippetshowstheByFactortype:

//ByFactorfunctiontypetypeByFactorfunc(Thing1*Thing,Thing2*Thing)bool

TheSortmethod

TheSortmethodisafunctionwiththebyFactorparameter,asshownhere://Sortmethodfunc(byFactorByFactor)Sort(Things[]Thing){varsortedThings*ThingSortersortedThings=&ThingSorter{Things:Things,byFactor:byFactor,}sort.Sort(sortedThings)}

ThingsorterclassTheThingsortersortstheelementsbytheirproperties.TheThingSorterclasshasanarrayofthingsandabyFactormethod:

//ThingSorterclasstypeThingSorterstruct{Things[]ThingbyFactorfunc(Thing1*Thing,Thing2*Thing)bool}

Thenextsectiontalksabouttheimplementationofthelen,swap,andlessmethods.

Thelen,swap,andlessmethodsThesort.Interfacehasthelen,swap,andlessmethods,asshowninthefollowingcode:

//Lenmethodfunc(ThingSorter*ThingSorter)Len()int{returnlen(ThingSorter.Things)}

//Swapmethodfunc(ThingSorter*ThingSorter)Swap(iint,jint){ThingSorter.Things[i],ThingSorter.Things[j]=ThingSorter.Things[j],ThingSorter.Things[i]}

//Lessmethodfunc(ThingSorter*ThingSorter)Less(iint,jint)bool{returnThingSorter.byFactor(&ThingSorter.Things[i],&ThingSorter.Things[j])}

Themainmethod

Themainmethodcreatesthingsandinitializesthemwithvalues.Thismethodshowsthingsthataresortedbymass,distance,andnameindecreasingorderofdistance:

//Mainmethodfuncmain(){varThings=[]Thing{{"IronRod",0.055,0.4,3000,-180},{"SteelChair",0.815,0.7,4000,-209},{"CopperBowl",1.0,1.0,60,-30},{"BrassPot",0.107,1.5,10000,-456},}

varnamefunc(*Thing,*Thing)boolname=func(Thing1*Thing,Thing2*Thing)bool{returnThing1.name<Thing2.name}varmassfunc(*Thing,*Thing)boolmass=func(Thing1*Thing,Thing2*Thing)bool{returnThing1.mass<Thing2.mass}vardistancefunc(*Thing,*Thing)booldistance=func(Thing1*Thing,Thing2*Thing)bool{returnThing1.distance<Thing2.distance}vardecreasingDistancefunc(*Thing,*Thing)booldecreasingDistance=func(p1,p2*Thing)bool{returndistance(p2,p1)}

ByFactor(name).Sort(Things)fmt.Println("Byname:",Things)ByFactor(mass).Sort(Things)fmt.Println("Bymass:",Things)ByFactor(distance).Sort(Things)fmt.Println("Bydistance:",Things)ByFactor(decreasingDistance).Sort(Things)fmt.Println("Bydecreasingdistance:",Things)}

Runthefollowingcommandtoexecutethesort_keys.gofile:gorunsort_keys.go

Thisistheoutput:

Thenextsectiontalksaboutthestructdatastructure.

ThestructtypeAstructtype(class)canbesortedusingdifferentsetsofmultiplefields.Inthesort_multi_keys.gocode,weshowhowtosortstructtypes.AclasscalledCommitconsistsoftheusername,lang,andnumlinesproperties.usernameisastring,langisastring,andnumlinesisaninteger.Inthefollowingcode,theCommitclassissortedbycommitsandlines:

///mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingfmtandsortpackageimport("fmt""sort")

//ACommitisarecordofcodecheckingtypeCommitstruct{usernamestringlangstringnumlinesint}

Inthenextsection,theimplementationofthemultiSorterclassisdiscussed.

ThemultiSorterclassThemultiSorterclassconsistsofthecommitsandlessFunctionarrayproperties.ThemultiSorterclassimplementstheSortinterfacetosortthecommits,asshowninthefollowingcode:

typelessFuncfunc(p1*Commit,p2*Commit)bool

//multiSorterclass

typemultiSorterstruct{

Commits[]Commit

lessFunction[]lessFunc

}

ThedifferentmethodsofthemultiSorterclassarediscussedinthefollowingsections.

TheSortmethod

Inthefollowingcodesnippet,theSortmethodofmultiSortersortstheCommitsarraybyinvokingsort.SortandpassingthemultiSorterargument:

//Sortmethod

func(multiSorter*multiSorter)Sort(Commits[]Commit){

multiSorter.Commits=Commits

sort.Sort(multiSorter)

}

TheOrderBymethod

TheOrderedBymethodtakesthelessfunctionandreturnsmultiSorter.Themultisorterinstanceisinitializedbythelessfunction,asshowninthefollowingcodesnippet:

//OrderedBymethod

funcOrderedBy(lessFunction...lessFunc)*multiSorter{

return&multiSorter{

lessFunction:lessFunction,

}

}

Thelenmethod

ThelenmethodofthemultiSorterclassreturnsthelengthoftheCommitsarray.TheCommitsarrayisapropertyofmultiSorter:

//Lenmethodfunc(multiSorter*multiSorter)Len()int{

returnlen(multiSorter.Commits)

}

TheSwapmethod

TheSwapmethodofmultiSortertakestheintegersiandjasinput.Thismethodswapsthearrayelementsatindexiandj:

//Swapmethodfunc(multiSorter*multiSorter)Swap(iint,jint){

multiSorter.Commits[i]=multiSorter.Commits[j]

multiSorter.Commits[j]=multiSorter.Commits[i]

}

Thelessmethod

TheLessmethodofthemultiSorterclasstakestheintegersiandjandcomparestheelementatindexitotheelementatindexj:

func(multiSorter*multiSorter)Less(iint,jint)bool{

varp*Commitvarq*Commitp=&multiSorter.Commits[i]q=&multiSorter.Commits[j]

varkintfork=0;k<len(multiSorter.lessFunction)-1;k++{less:=multiSorter.lessFunction[k]switch{caseless(p,q):returntruecaseless(q,p):returnfalse}}returnmultiSorter.lessFunction[k](p,q)}

Themainmethod

ThemainmethodcreatesaCommitarrayandinitializesthearraywithvalues.Functionsarecreatedforsortingbyuser,language,andlines.OrderedByreturnsamultiSorter,anditssortmethodiscalledbyuser,language,increasingLines,anddecreasingLines:

//mainmethodfuncmain(){varCommits=[]Commit{{"james","Javascript",110},{"ritchie","python",250},{"fletcher","Go",300},{"ray","Go",400},{"john","Go",500},{"will","Go",600},{"dan","C++",500},{"sam","Java",650},{"hayvard","Smalltalk",180},}varuserfunc(*Commit,*Commit)booluser=func(c1*Commit,c2*Commit)bool{returnc1.username<c2.username}varlanguagefunc(*Commit,*Commit)boollanguage=func(c1*Commit,c2*Commit)bool{returnc1.lang<c2.lang}varincreasingLinesfunc(*Commit,*Commit)boolincreasingLines=func(c1*Commit,c2*Commit)bool{returnc1.numlines<c2.numlines}vardecreasingLinesfunc(*Commit,*Commit)booldecreasingLines=func(c1*Commit,c2*Commit)bool{returnc1.numlines>c2.numlines//Note:>ordersdownwards.}OrderedBy(user).Sort(Commits)fmt.Println("Byusername:",Commits)OrderedBy(user,increasingLines).Sort(Commits)fmt.Println("Byusername,ascorder",Commits)OrderedBy(user,decreasingLines).Sort(Commits)fmt.Println("Byusername,descorder",Commits)OrderedBy(language,increasingLines).Sort(Commits)fmt.Println("Bylang,ascorder",Commits)OrderedBy(language,decreasingLines,user).Sort(Commits)fmt.Println("Bylang,descorder",Commits)}

Runthefollowingcommandtoexecutethesort_multi_keys.gofile:gorunsort_multi_keys.go

Thisistheoutput:

ThenextsectiontalksabouttheHTMLunorderedlistdatastructure.

UnorderedlistsAnunorderedlistisimplementedasalinkedlist.Inanunorderedlist,therelativepositionsofitemsincontiguousmemorydon'tneedtobemaintained.Thevalueswillbeplacedinarandomfashion.Anunorderedliststartswitha<ul>taginHTML5.0.Eachlistitemiscodedwith<li>tags.Here'sanexample:

<ul><li>Firstbook</li><li>Secondbook</li><li>Thirdbook</li></ul>

ThefollowingisanexampleofanunorderedlistinGolang.TheNodeclasshasapropertyandanextNodepointer,asshowninthefollowingcode.Thelinkedlistwillhaveasetofnodeswithapropertyattribute.Theunorderedlistispresentedinthescriptcalledunordered_list.go:

//mainpackagehasexamplesshown//inHands-OnDataStructuresandalgorithmswithGobookpackagemain

//importingfmtpackageimport("fmt")

//NodeclasstypeNodestruct{propertyintnextNode*Node}

ThenextsectiontalksabouttheUnOrderedListclassimplementation.

TheUnOrderedListclassTheunorderedlistconsistsofelementsthatarenotorderedbynumbers.AnUnOrderedListclasshasaheadNodepointerastheproperty.Traversingtothenextnodefromtheheadnode,youcaniteratethroughthelinkedlist:

//UnOrderedListclass

typeUnOrderedListstruct{

headNode*Node

}

ThenextsectiondiscussestheAddtoHeadmethodandtheIterateListmethodoftheUnOrderedListstruct.

TheAddtoHeadmethod

TheAddtoHeadmethodaddsthenodetotheheadoftheunorderedlist.TheAddToHeadmethodoftheUnOrderedListclasshasapropertyparameterthat'saninteger.ItwillmaketheheadNodepointtoanewnodecreatedwithproperty,andthenextNodepointstothecurrentheadNodeoftheunorderedlist:

//AddToHeadmethodofUnOrderedListclassfunc(UnOrderedList*UnOrderedList)AddToHead(propertyint){varnode=&Node{}node.property=propertynode.nextNode=nilifUnOrderedList.headNode!=nil{node.nextNode=UnOrderedList.headNode}UnOrderedList.headNode=node}

TheIterateListmethod

TheIterateListmethodoftheUnOrderedListclassprintsthenodepropertyofthenodesinthelist.Thisisshowninthefollowingcode:

//IterateListmethoditeratesoverUnOrderedListfunc(UnOrderedList*UnOrderedList)IterateList(){varnode*Nodefornode=UnOrderedList.headNode;node!=nil;node=node.nextNode{fmt.Println(node.property)}}

Themainmethod

Themainmethodcreatesaninstanceofalinkedlist,andintegerproperties1,3,5,and7areaddedtotheheadofthelinkedlist.Thelinkedlist'sheadNodepropertyisprintedaftertheelementsareadded:

//mainmethodfuncmain(){varunOrderedListUnOrderedListunOrderedList=UnOrderedList{}unOrderedList.AddToHead(1)unOrderedList.AddToHead(3)unOrderedList.AddToHead(5)unOrderedList.AddToHead(7)unOrderedList.IterateList()}

Runthefollowingcommandtoexecutetheunordered_list.gofilefromthecodebundle:

gorununordered_list.go

Thisistheoutput:

SummaryThischaptercoveredheterogeneousdatastructuressuchasorderedlistsandunorderedlistswithcodeexamples.TheOrderedlistssectioncoveredsortingslicesbysinglekey,multiplekeys,andsort.Slice.Slicesaresortedbymakingthearrayofstructelementsimplementthesort.Sortinterface.Unorderedlistsweredescribedaslinkedlistswithvaluesthatarenotordered.Thenextchapterwillcoverdynamicdatastructuressuchasdictionaries,TreeSets,sequences,synchronizedTreeSets,andmutableTreeSets.

Questions1. Whichmethodofthesort.Sortinterfacereturnsthesizeoftheelementstobesorted?

2. Whichfunctionneedstobepassedtothesort.Slicemethodtosortaslice?

3. Whatdoestheswapmethoddototheelementsattheiandjindices?4. Whatisthedefaultorderforsortingelementsusingsort.Sort?5. Howdoyouimplementascendinganddescendingsortingwith

sort.Slice?6. Howdoyousortanarrayandkeeptheoriginalorderoftheelements?7. Whichinterfaceisusedtoreversetheorderofthedata?8. Showanexampleofsortingaslice.9. Whichmethodiscalledtoaddelementstoanunorderedlist?10. Writeacodeexampleofanunorderedlistoffloats.

Furtherreading

Thefollowingbooksarerecommendedifyouwanttoknowmoreaboutheterogeneousdatastructures:

DesignPatterns, byErichGamma,RichardHelm,RalphJohnson,andJohnVlissidesIntroductiontoAlgorithms –ThirdEdition,byThomasH.Cormen,CharlesE.Leiserson,RonaldL.Rivest,andCliffordSteinDatastructuresandAlgorithms:AnEasyIntroduction,by RudolphRussell

DynamicDataStructuresAdynamicdatastructureisasetofelementsinmemorythathastheadaptabilitytoexpandorshrink.Thisabilityempowersasoftwareengineertocontrolpreciselyhowmuchmemoryisused.Dynamicdatastructuresareusedforhandlinggenericdatainakey-valuestore.Theycanbeusedindistributedcachingandstoragemanagement.Dynamicdatastructuresarevaluableinmanycircumstancesinwhichdynamicadditionordeletionofelementsoccur.Theyarecomparableincapacitytoasmallerrelationaldatabaseoranin-memorydatabase.Thesedatastructuresareusedinmarketingandcustomerrelationshipmanagementapplications.Dictionaries,TreeSets,andsequencesareexamplesofdynamicdatastructures.Inthischapter,wewillexplainwhatdictionaries,TreeSets,andsequencesareandshowyouhowtheyareimplementedwiththehelpofcodeexamples.  Thischaptercoversthefollowing dynamicdatastructures:

DictionariesTreeSets:

SynchronizedTreeSetsMutableTreeSets

Sequences:

FareyFibonacciLook-and-sayThue–Morse

TechnicalrequirementsInstallGoVersion1.10fromhttps://golang.org/doc/install foryourOS.TheGitHubURLforthecodeinthischapterisasfollows: https://github.com/PacktPublishing/Learn-Data-Structures-and-Algorithms-with-Golang/tree/master/Chapter07.

DictionariesAdictionaryisacollectionofuniquekeyandvaluepairs. Adictionaryisabroadlyusefuldatastructureforstoringasetofdataitems.Ithasakey,andeachkeyhasasolitaryitemassociatedwithit.Whengivenakey,thedictionarywillrestoretheitemassociatedwiththatkey.Thesekeyscanbeofanytype:strings,integers,orobjects.Whereweneedtosortalist,anelementvaluecanberetrievedutilizingitskey. Add,remove,modify,andlookupoperationsareallowedinthiscollection.Adictionaryissimilartootherdatastructures,suchashash,map,andHashMap.Thekey/valuestoreisusedindistributedcachingandinmemorydatabases.Arraysdifferfromdictionariesinhowthedataisaccessed.Asethasuniqueitems,whereasadictionarycanhaveduplicatevalues.Dictionarydatastructuresareusedinthefollowingstreams:

PhonedirectoriesRoutertablesinnetworkingPagetablesinoperatingsystemsSymboltablesincompilersGenomemapsinbiology

Thefollowingcodeshowshowtoinitializeandmodifyadictionary. Inthissnippet,thedictionaryhasthekeyDictKeyandisastring:

//mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingfmtpackageimport("fmt""sync")

//DictKeytypetypeDictKeystring

Thefollowingsectionstalkaboutthetypeandmethodsindictionaries.

DictValtypeThedictionaryhasthevalueDictValoftypestringmappedtoDictKey:

//DictValtypetypeDictValstring

DictionaryclassThedictionaryinthefollowingcodeisaclasswithdictionary elements,withDictKeyas the key andDictValasthevalue.Ithasa sync.RWMutexproperty, lock:

//DictionaryclasstypeDictionarystruct{elementsmap[DictKey]DictVallocksync.RWMutex}

The Put, Remove, Contain, Find, Rest, NumberofElements,GetKeys,GetValues, andMain methodsarediscussedinthefollowingsections.

Putmethod

AhasaPutmethod,asshowninthefollowingexample,thattakesthekeyandvalueparameters oftheDictKeyandDictVal typesrespectively.TheLockmethod ofthedictionary'slockinstanceisinvoked,andtheUnlockmethodisdeferred.Ifthereareemptymapelementsinthedictionary,elementsareinitializedusingmake.The map elementsaresetwithakeyandavalueiftheyarenotempty:

//Putmethodfunc(dict*Dictionary)Put(keyDictKey,valueDictVal){dict.lock.Lock()deferdict.lock.Unlock()ifdict.elements==nil{dict.elements=make(map[DictKey]DictVal)}dict.elements[key]=value}

Theexampleoutputoftheputmethodisasfollows.Theputmethodtakesthekey1andvalue1.Themapisupdatedwithkeyandvalue:

Removemethod

Adictionaryhasaremovemethod,asshowninthefollowingcode,whichhasakeyparameter oftheDictKey type.ThismethodreturnsaboolvalueifthevalueassociatedwithDictkeyisremovedfromthe map:

//Removemethodfunc(dict*Dictionary)Remove(keyDictKey)bool{dict.lock.Lock()deferdict.lock.Unlock()varexistsbool_,exists=dict.elements[key]ifexists{delete(dict.elements,key)}returnexists}

Containsmethod

Inthefollowingcode, the Containsmethodhasaninputparameter,key,oftheDictKey type,andreturns boolif keyexistsinthedictionary:

//Containsmethodfunc(dict*Dictionary)Contains(keyDictKey)bool{dict.lock.RLock()deferdict.lock.RUnlock()varexistsbool_,exists=dict.elements[key]returnexists}

Findmethod

TheFindmethodtakesthekeyparameter oftheDictKeytype andreturnstheDictVal typeassociatedwiththekey.ThefollowingcodesnippetexplainstheFindmethod:

//Findmethodfunc(dict*Dictionary)Find(keyDictKey)DictVal{dict.lock.RLock()deferdict.lock.RUnlock()returndict.elements[key]}

Resetmethod

TheResetmethodoftheDictionaryclassispresentedinthefollowingsnippet.TheLockmethod ofthedictionary'slockinstance isinvokedandUnlockisdeferred.Theelementsmapisinitializedwithamapof the DictKeykeyandthe DictValvalue:

//Resetmethodfunc(dict*Dictionary)Reset(){dict.lock.Lock()deferdict.lock.Unlock()dict.elements=make(map[DictKey]DictVal)}

NumberOfElementsmethod

TheNumberOfElementsmethodoftheDictionaryclassreturnsthelengthoftheelementsmap.TheRLockmethodofthelockinstanceisinvoked.TheRUnlockmethodofthelockinstanceisdeferredbeforereturningthelength;thisisshowninthefollowingcodesnippet:

//NumberOfElementsmethodfunc(dict*Dictionary)NumberOfElements()int{dict.lock.RLock()deferdict.lock.RUnlock()returnlen(dict.elements)}

GetKeysmethod

TheGetKeysmethodoftheDictionaryclassisshowninthefollowingcodesnippet.Themethodreturnsthearrayofthe DictKeyelements.TheRLockmethodofthelockinstanceisinvoked,andtheRUnlockmethodisdeferred.Thedictionarykeysarereturnedbytraversingtheelement'smap:

//GetKeysmethodfunc(dict*Dictionary)GetKeys()[]DictKey{dict.lock.RLock()deferdict.lock.RUnlock()vardictKeys[]DictKeydictKeys=[]DictKey{}varkeyDictKeyforkey=rangedict.elements{dictKeys=append(dictKeys,key)}returndictKeys}

GetValuesmethod

TheGetValuesmethodoftheDictionaryclassreturnsthearrayofthe DictValelements.Inthefollowingcodesnippet,theRLockmethodofthelockinstanceisinvokedandtheRUnlockmethodisdeferred.Thearrayofdictionaryvaluesisreturnedaftertraversingtheelement'smap:

//GetValuesmethodfunc(dict*Dictionary)GetValues()[]DictVal{dict.lock.RLock()deferdict.lock.RUnlock()vardictValues[]DictValdictValues=[]DictVal{}varkeyDictKeyforkey=rangedict.elements{dictValues=append(dictValues,dict.elements[key])}returndictValues}

Themainmethod

Thefollowingcodeshowsthemainmethod,wherethedictionaryisinitializedandprinted:

//mainmethodfuncmain(){vardict*Dictionary=&Dictionary{}dict.Put("1","1")dict.Put("2","2")dict.Put("3","3")dict.Put("4","4")fmt.Println(dict)}

Runthefollowingcommandstoexecutethedictionary.gofile:gorundictionary.go

Theoutputisasfollows:

Let'stakealookattheTreeSetdatastructureinthefollowingsection.

TreeSetsTreeSetsareusedinmarketingandcustomerrelationshipmanagementapplications.TreeSetisasetthathasabinarytreewithuniqueelements.Theelementsaresortedinanaturalorder.Inthefollowingcodesnippet,TreeSetcreation,insertion,search,andstringifyoperationsarepresented.TreeSetallowsonlyonenullvalueifthesetisempty.Theelementsaresortedandstoredaselements.Theadd,remove,andcontainsfunctionscostlog(n)onTreeSets:

///mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//TreeSetclasstypeTreeSetstruct{bst*BinarySearchTree}

WewilldiscussthedifferentTreeSetmethodsinthefollowingsections.

InsertTreeNodemethod

TheInsertTreeNodemethod oftheTreeSetclasstakestreeNodes variableargumentsoftheTreeNodetype.Inthefollowingcode,theelementswiththekeyandvalueareinsertedinthebinarysearchtreeof TreeSet:

//InsertTreeNodemethodfunc(treeset*TreeSet)InsertTreeNode(treeNodes...TreeNode){vartreeNodeTreeNodefor_,treeNode=rangetreeNodes{treeset.bst.InsertElement(treeNode.key,treeNode.value)}}

Theexampleoutputofthe InsertTreeNodemethodisasfollows.TheInsertTreeNodemethodtakestreeNodesastheparameter.treeNodesareinsertedwithrootNode,whichhasavalueof 8:

Deletemethod

TheDeletemethodoftheTreeSetclassisshowninthefollowingcodesnippet.Inthismethod,treeNodeswiththeprovidedkeyareremoved:

//Deletemethodfunc(treeset*TreeSet)Delete(treeNodes...TreeNode){vartreeNodeTreeNodefor_,treeNode=rangetreeNodes{treeset.bst.RemoveNode(treeNode.key)}}

InOrderTraverseTreemethod

TheInOrderTraverseTreemethodoftheBinarySearchTreeclasstakesfunctionasaparameter.TheRLockmethodofthelockinstanceisinvoked.The RUnlockmethodofthetree'slockinstanceisdeferred.InOrderTraverseTreeisinvokedwiththerootNodeofthetreeandfunctionasparameters:

//InOrderTraverseTreemethodfunc(tree*BinarySearchTree)InOrderTraverseTree(functionfunc(int)){tree.lock.RLock()defertree.lock.RUnlock()inOrderTraverseTree(tree.rootNode,function)}

TheinOrderTraverseTreemethod

TheinOrderTraverseTreemethodtraversesfromtheleftofthetreetorootofthenodeandthentotherightofthetree.TheinOrderTraverseTreemethodtakestreeNodeandfunctionasparameters.ThemethodrecursivelycallstheinOrderTraverseTreemethodwithfunctionandthenleftNodeandrightNodeinseparatecalls.ThefunctionmethodisinvokedwiththevalueoftreeNode:

//inOrderTraverseTreemethodfuncinOrderTraverseTree(treeNode*TreeNode,functionfunc(int)){iftreeNode!=nil{inOrderTraverseTree(treeNode.leftNode,function)function(treeNode.value)inOrderTraverseTree(treeNode.rightNode,function)}}

PreOrderTraverseTreemethod

ThePreOrderTraverseTreemethodoftheBinarySearchTreeclasstakesthefunctionasitsparameter.TheLockmethodonthetree'slockinstanceisinvokedfirst,andtheUnlockmethodisdeferred.ThePreOrderTraverseTreemethodiscalledwiththerootNodeofthetreeandfunctionasparameters:

//PreOrderTraversemethodfunc(tree*BinarySearchTree)PreOrderTraverseTree(functionfunc(int)){tree.lock.Lock()defertree.lock.Unlock()preOrderTraverseTree(tree.rootNode,function)}

ThepreOrderTraverseTreemethod

ThepreOrderTraverseTreemethodtraversesthetreefromtheroot,totheleftandrightofthetree.ThepreOrderTraverseTreemethodtakestreeNodeandfunctionasparameters.IftreeNodeisnotnil,functionisinvokedwiththevalueoftreeNode,andthepreOrderTraverseTreemethodisinvokedwithfunction andleftNodeandrightNodeasparameters:

//preOrderTraverseTreemethodfuncpreOrderTraverseTree(treeNode*TreeNode,functionfunc(int)){iftreeNode!=nil{function(treeNode.value)preOrderTraverseTree(treeNode.leftNode,function)preOrderTraverseTree(treeNode.rightNode,function)}}

Searchmethod

TheSearchmethodoftheTreeSetclasstakesa variableargumentnamedtreeNodesoftheTreeNodetype andreturnstrueifoneofthosetreeNodesexists;otherwise,itreturnsfalse.ThecodefollowingsnippetoutlinestheSearchmethod:

//Searchmethodfunc(treeset*TreeSet)Search(treeNodes...TreeNode)bool{vartreeNodeTreeNodevarexistsboolfor_,treeNode=rangetreeNodes{ifexists=treeset.bst.SearchNode(treeNode.key);!exists{returnfalse}}returntrue}

TheStringmethod

Inthefollowingcodesnippet,theStringmethodoftheTreeSetclassreturnsthestringversionofbst:

//Stringmethodfunc(treeset*TreeSet)String(){treeset.bst.String()}

Themainmethod

ThemainmethodintheTreeSetclasscreatesaTreeSetwithTreeNodes.ThefollowingsnippetcreatesaTreeSetandinvokestheStringmethod:

//mainmethodfuncmain(){vartreeset*TreeSet=&TreeSet{}treeset.bst=&BinarySearchTree{}varnode1TreeNode=TreeNode{8,8,nil,nil}varnode2TreeNode=TreeNode{3,3,nil,nil}varnode3TreeNode=TreeNode{10,10,nil,nil}varnode4TreeNode=TreeNode{1,1,nil,nil}varnode5TreeNode=TreeNode{6,6,nil,nil}treeset.InsertTreeNode(node1,node2,node3,node4,node5)treeset.String()}

Runthefollowingcommands toexecutethe treeset.go andbinarysearchtree.gofiles:

$gobuildtreeset.gobinarysearchtree.go

$./treeset

Theoutputisasfollows:

ThenextsectiontalksaboutthesynchronizedTreeSetdatastructure.

SynchronizedTreeSetsOperationsthatareperformedonsynchronizedTreeSetsaresynchronizedacrossmultiplecallsthataccesstheelementsofTreeSets.SynchronizationinTreeSetsisachievedusingasync.RWMutexlock.Thelockmethodonthetree'slockinstanceisinvoked,andtheunlockmethodisdeferredbeforethetreenodesare inserted,deleted,orupdated:

//InsertElementmethodfunc(tree*BinarySearchTree)InsertElement(keyint,valueint){tree.lock.Lock()defertree.lock.Unlock()vartreeNode*TreeNodetreeNode=&TreeNode{key,value,nil,nil}iftree.rootNode==nil{tree.rootNode=treeNode}else{insertTreeNode(tree.rootNode,treeNode)}}

Mutable TreeSetsMutableTreeSetscanuseadd,update,anddeleteoperationsonthetreeanditsnodes.insertTreeNodeupdatesthetreebytakingtherootNodeandtreeNodeparameters tobeupdated.ThefollowingcodesnippetshowshowtoinsertaTreeNodewithagivenrootNodeandTreeNode:

//insertTreeNodemethodfuncinsertTreeNode(rootNode*TreeNode,newTreeNode*TreeNode){ifnewTreeNode.key<rootNode.key{ifrootNode.leftNode==nil{rootNode.leftNode=newTreeNode}else{insertTreeNode(rootNode.leftNode,newTreeNode)}}else{ifrootNode.rightNode==nil{rootNode.rightNode=newTreeNode}else{insertTreeNode(rootNode.rightNode,newTreeNode)}}}

Let'sdiscussthedifferentmutableTreeSetsinthefollowingsections.

RemoveNodemethod

TheRemoveNodemethodofaBinarySearchTreeisasfollows://RemoveNodemethodfunc(tree*BinarySearchTree)RemoveNode(keyint){tree.lock.Lock()defertree.lock.Unlock()removeNode(tree.rootNode,key)}

Treeset.bstTheTreeNode'scanbeupdatedbyaccessingtreeset.bstandtraversingthebinarysearchtreefromtherootNodeandtheleftandright nodesofrootNode,asshownhere:

vartreeset*TreeSet=&TreeSet{}treeset.bst=&BinarySearchTree{}varnode1TreeNode=TreeNode{8,8,nil,nil}varnode2TreeNode=TreeNode{3,3,nil,nil}varnode3TreeNode=TreeNode{10,10,nil,nil}varnode4TreeNode=TreeNode{1,1,nil,nil}varnode5TreeNode=TreeNode{6,6,nil,nil}treeset.InsertTreeNode(node1,node2,node3,node4,node5)treeset.String()

Inthenextsection,wewilltakealookatsequences.

SequencesAsequenceisasetofnumbersthataregroupedinaparticularorder.Thenumberofelementsinthestreamcanbeinfinite,andthesesequencesarecalledstreams.Asubsequenceisasequencethat'screatedfromanothersequence.Therelativepositionsoftheelementsinasubsequencewillremainthesameafterdeletingsomeoftheelementsinasequence.Inthefollowingsections,wewilltakealookatdifferentsequencessuchastheFareysequence,Fibonaccisequence,look-and-say,andThue–Morse.

FareysequenceAFareysequenceconsistsofreducedfractionswithvaluesbetweenzeroandone.Thedenominatorsofthefractionsarelessthanorequaltom,andorganizedinascendingorder.ThissequenceiscalledaFareyseries.Inthefollowingcode,reducedfractionsaredisplayed:

///mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain//importingfmtpackageimport("fmt")

//fractionclasstypefractionstruct{numeratorintdenominatorint}

Let'stakealookatthedifferentmethodsinaFareysequence.

Stringmethod

Thefractionclasshasthenumeratoranddenominator integerproperties.TheStringmethodofthefractionclass,asshowninthefollowingsnippet,returnsastringversionof fraction:

//stringmethodoffractionclassfunc(fracfraction)String()string{returnfmt.Sprintf("%d/%d",frac.numerator,frac.denominator)}

Theg method

Thegmethodtakestwofractionsandprintstheseriesofreducedfractions.Thegfunction takesan loran rfraction,andnum intas argumentstoprintthereducedfractionasaseries.Thefollowingcodesnippetshowsthegmethod:

//gmethodfuncg(lfraction,rfraction,numint){varfracfractionfrac=fraction{l.numerator+r.numerator,l.denominator+r.denominator}iffrac.denominator<=num{g(l,frac,num)fmt.Print(frac,"")g(frac,r,num)}}

Themainmethod

Thefollowingsnippetshowsthemainmethod.Inthemainmethod,reducedfractionseriesareprintedusingrecursion:

//mainmethodfuncmain(){varnumintvarlfractionvarrfractionfornum=1;num<=11;num++{l=fraction{0,1}r=fraction{1,1}fmt.Printf("F(%d):%s",num,l)g(l,r,num)fmt.Println(r)}

Runthefollowingcommandtoexecutethefarey_sequence.gofile:gorunfarey_sequence.go

Theoutputisasfollows:

ThenextsectiontalksabouttheFibonaccisequencedatastructure.

FibonaccisequenceTheFibonaccisequenceconsistsofalistofnumbersinwhicheverynumberisthesumofthetwoprecedingnumbers.Pingala,in200BC,wasthefirsttocomeupwithFibonaccinumbers.TheFibonaccisequenceisasfollows:

TherecurrencerelationfortheFibonaccisequenceisasfollows:

Theseedvaluesareasfollows:

AFibonacciprimeisaFibonaccinumberthatisaprimenumber.The

AFibonacciprimeisaFibonaccinumberthatisaprimenumber.TheFibonacciprimeseriesisasfollows:

ComputeralgorithmssuchastheFibonaccisearchtechnique,heap,andcubesarepopularapplicationsofFibonaccinumbers.PseudorandomnumbergeneratorsuseFibonaccinumbers.Thefollowingcodesnippet showstheFibonaccisequenceandrecursiveFibonaccinumbercalculation.TheSeriesfunctionispresentedaswell.TheSeriesfunctioncalculatestheFibonaccinumbersinthesequence:

///mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingfmtandstrconvpackageimport("fmt""strconv")

//SeriesmethodfuncSeries(nint)int{varf[]intf=make([]int,n+1,n+2)ifn<2{f=f[0:2]}f[0]=0f[1]=1variintfori=2;i<=n;i++{f[i]=f[i-1]+f[i-2]}returnf[n]}

ThedifferentmethodsoftheFibonaccisequencearediscussedinthefollowingsections.

FibonacciNumbermethod

TheFibonacciNumbermethodtakestheintegernand,byrecursion,calculatestheFibonaccinumbers.Thefollowingcodesnippetshowsthisrecursion:

//FibonacciNumbermethodfuncFibonacciNumber(nint)int{ifn<=1{returnn}returnFibonacciNumber(n-1)+FibonacciNumber(n-2)}

Mainmethod

ThemainmethodinthefollowingcodesnippetshowshowtheFibonaccisequenceiscalculated:

//mainmethodfuncmain(){variintfori=0;i<=9;i++{fmt.Print(strconv.Itoa(Series(i))+"")}fmt.Println("")fori=0;i<=9;i++{fmt.Print(strconv.Itoa(FibonacciNumber(i))+"")}fmt.Println("")}

Runthefollowingcommandtoexecutethefibonacci_sequence.gofile:gorunfibonacci_sequence.go

Theoutputisasfollows:

Thenextsectiontalksaboutthelook-and-saydatastructure.

Look-and-sayThelook-and-saysequenceisasequenceofintegers:

Thesequenceisgeneratedbycountingthedigitsofthepreviousnumberinthegroup.JohnConwayinitiallycoinedthetermlook-and-saysequence.Thelook-and-saysequenceisshowninthefollowingcode.Thelook_saymethodtakesastringasaparameterandreturnsalook-and-saysequenceofintegers:

//mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingfmtandstrconvpackageimport("fmt""strconv")

//look_saymethodfunclook_say(strstring)(rstrstring){varcbytebytecbyte=str[0]varincintinc=1variintfori=1;i<len(str);i++{vardbytebytedbyte=str[i]ifdbyte==cbyte{inc++continue}rstr=rstr+strconv.Itoa(inc)+string(cbyte)cbyte=dbyte

cbyte=dbyte

inc=1}returnrstr+strconv.Itoa(inc)+string(cbyte)}

Themainmethodinitializesthe stringandinvokesthelook_saymethod.Thelook-and-saysequencethatisreturnedfromthemethodisprinted:

//mainmethodfuncmain(){varstrstringstr="1"fmt.Println(str)variintfori=0;i<8;i++{str=look_say(str)fmt.Println(str)}}

Runthefollowingcommandtoexecutethelook_say.gofile:gorunlook_say.go

Theoutputisasfollows:

ThenextsectiontalksabouttheThue–Morsedatastructure.

Thue–MorseThe Thue–MorsesequenceisabinarysequencestartingatzerothatappendstheBooleancomplementofthecurrentsequence.TheThue–Morsesequence isasfollows:

TheThue–MorsesequencewasappliedbyEugeneProphetandusedbyAxelThueinthestudyofcombinatoricsonwords.TheThue–Morsesequenceisusedintheareaoffractalcurves,suchasKochsnowflakes.ThefollowingcodesnippetcreatestheThue–Morsesequence.TheThueMorseSequencefunction takesabytes.BufferinstancebufferandmodifiesthebuffertotheThue–Morsesequencebyapplyingthecomplementoperationonthebytes:

//mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingfmtandbytespackageimport("bytes""fmt")

//ThueMorseSequencemethodfuncThueMorseSequence(buffer*bytes.Buffer){

varbintvarcurrLengthintvarcurrBytes[]byteforb,currLength,currBytes=0,buffer.Len(),buffer.Bytes();b<currLength;b++{ifcurrBytes[b]=='1'{buffer.WriteByte('0')

buffer.WriteByte('0')

}else{buffer.WriteByte('1')}}}

Themainmethodinitializesthesequencenumberas0.TheThueMorseSequencemethodtakesthepointertothebytes.BufferandmodifiesitbyinvokingtheThueMorseSequencemethod.TheresultingsequenceisprintedontheTerminal:

//mainmethodfuncmain(){varbufferbytes.Buffer//initialsequencememberis"0"buffer.WriteByte('0')fmt.Println(buffer.String())variintfori=2;i<=7;i++{ThueMorseSequence(&buffer)fmt.Println(buffer.String())}}

Runthefollowingcommandtoexecutethethue_morse.gofile:gorunthue_morse.go

Theoutputisasfollows:

SummaryThischaptercoveredthecontains,put,remove,find,reset,NumberOfElements,getKeys,andgetValuesmethodsofthedictionarydatastructure.TheInsertTreeNode,Delete,Search,andstringifyTreeSetoperations havebeen explainedindetail,andcodeexampleswereprovided.TheBinarySearchTreestructurehasbeenpresentedincode,alongwiththeInsertElement,InOrderTraversal,PreOrderTraverseTree,SearchNode,andRemoveNodefunctions.Thenextchaptercoversalgorithmssuchassorting,searching,recursion,andhashing.

Questions1. HowdoyouensureaBinarySearchTreeissynchronized?2. Whichmethodiscalledtopostponetheinvocationofafunction?3. Howdoyoudefinedictionarykeysandvalueswithcustomtypes?4. Howdoyoufindthelengthofamap?5. WhatkeywordisusedtotraversealistoftreeNodesinatree?6. InaFareysequence,whataretherealnumbersintheseriescalled?7. WhatisaFibonaccinumber?8. Howdoyouconvertanintegerintoastring?9. Whatmethodisusedtoconvertabyteintoastring?10. Whatmethodiscalledtoaddelementstoadictionary?

Furtherreading

Thefollowingbooksarerecommendedifyouwanttolearnmoreaboutdynamicdatastructures:

DesignPatterns, byErichGamma,RichardHelm,RalphJohnson,andJohnVlissidesIntroductiontoAlgorithms –ThirdEdition,byThomasH.Cormen,CharlesE.Leiserson,RonaldL.Rivest,andCliffordSteinDatastructuresandAlgorithms:AnEasyIntroduction,by RudolphRussell

ClassicAlgorithmsClassicalgorithmsareusedintheareasofdatasearchandcryptography.Sorting,searching,recursing,andhashingalgorithmsaregoodexamplesofclassicalgorithms. Sortingalgorithmsareusedtoorderelementsintoeitheranascendingordescending keyarrangement.Thesealgorithmsarefrequentlyusedtocanonicalizedataandtocreatereadablecontent.Searchalgorithmsareusedtofindanelementinaset.Arecursivealgorithmisonethatcallsitselfwithinputitems. Ahashingalgorithmisacryptographichashtechnique.Itisascientificcalculationthatmapsdatawithasubjectivesizetoahashwithasettledsize.It'sintendedtobeasingledirectionfunction,thatyoucannotalter.Inthischapter,wewillcoverthedifferentclassicalgorithmsandexplainthemwithsuitableexamples.Thischaptercoversthefollowingalgorithms:

Sorting:BubbleSelectionInsertionShellMergeQuick

Searching:LinearSequentialBinaryInterpolation

RecursionHashing

TechnicalrequirementsInstallGoversion1.10fromhttps://golang.org/doc/installforyourOS.TheGitHubURLforthecodeinthischapterisasfollows: https://github.com/PacktPublishing/Learn-Data-Structures-and-Algorithms-with-Golang/tree/master/Chapter08.

Sorting

Sortingalgorithmsarrangetheelementsinacollectioninascendingordescendingorder.Lexicographicalordercanbeappliedtoacollectionofcharactersandstrings.Theefficiencyofthesealgorithmsisintheperformanceofsortingtheinputdataintoasortedcollection.Thebestsortingalgorithm timecomplexityisO(nlogn).Sorting algorithmsareclassifiedbythefollowingcriteria:

ComputationalcomplexityMemoryusageStabilityTypeofsorting:serial/parallelAdaptabilityMethodofsorting

Inthefollowingsections,we'lllookatthedifferentsortingalgorithms,thatis,bubble,selection,insertion,shell,merge,andquick.

BubbleThebubblesortalgorithmisasortingalgorithmthatcomparesapairofneighboringelementsandswapsthemiftheyareinthewrongorder.ThealgorithmhasacomplexityofO(n2),wherenisthenumberofelementstobesorted.Thesmallestorgreatestvaluebubblesuptothetopofthecollection,orthesmallestorgreatestsinkstothebottom(dependingonwhetheryou'resortingintoascendingordescendingorder).Thefollowingcodesnippetshowstheimplementationofthebubblesortalgorithm.ThebubbleSorterfunctiontakesanintegerarrayandsortsthearray'selementsinascendingorder. Themainmethodinitializesthearray'sintegersandinvokesthebubbleSorter function,asfollows:

//mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingfmtandbytespackageimport("fmt")

//bubbleSortermethodfuncbubbleSorter(integers[11]int){

varnumintnum=11varisSwappedboolisSwapped=trueforisSwapped{isSwapped=falsevariintfori=1;i<num;i++{ifintegers[i-1]>integers[i]{

vartemp=integers[i]integers[i]=integers[i-1]integers[i-1]=tempisSwapped=true}}}fmt.Println(integers)}

//mainmethodfuncmain(){varintegers[11]int=[11]int{31,13,12,4,18,16,7,2,3,0,10}fmt.Println("BubbleSorter")bubbleSorter(integers)

}

Runthefollowingcommandtoexecutethebubble_sort.gofile:gorunbubble_sort.go

Theoutputisasfollows:

Let'stakealookattheselectionsortalgorithminthefollowingsection.

Selection

Selectionsortisanalgorithmthatdividestheinputcollectionintotwofragments.Thissublistofelementsissortedbyswappingthesmallestorlargestelementfromtheleftofthelisttotheright.ThealgorithmisoftheorderO(n2).Thisalgorithmisinefficientforlargecollections,anditperformsworsethantheinsertionsortalgorithm.Thefollowingcodeshowstheimplementationofthe SelectionSorterfunction,whichtakesthecollectiontobesorted:

//mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingfmtpackageimport("fmt")

//SelectionSortermethodfuncSelectionSorter(elements[]int){

variintfori=0;i<len(elements)-1;i++{varminintmin=ivarjintforj=i+1;j<=len(elements)-1;j++{ifelements[j]<elements[min]{min=j}}swap(elements,i,min)}}

Let'stakealookatthedifferentselectionmethodsinthenextsections.

Theswapmethod

Theswapmethodtakestheelementsarrayandthe iandjindicesasparameters.Themethodswapstheelementatpositioniwiththeelementatposition j,asshownhere:

//swapmethodfuncswap(elements[]int,iint,jint){vartempinttemp=elements[j]elements[j]=elements[i]elements[i]=temp}

Themainmethod

Themainmethodinitializestheelementsarray.The elementsareprintedbeforeandaftersortinginthefollowingcodesnippet:

//mainmethodfuncmain(){varelements[]intelements=[]int{11,4,18,6,19,21,71,13,15,2}fmt.Println("BeforeSorting",elements)SelectionSorter(elements)fmt.Println("AfterSorting",elements)}

Runthefollowingcommand toexecutetheselection_sort.gofile:gorunselection_sort.go

Theoutputisasfollows:

Let'stakealookattheinsertionsortalgorithminthefollowingsection.

Insertion

Insertionsortisanalgorithmthatcreatesafinalsortedarrayoneelementatatime.Thealgorithm'sperformanceisoftheorderO(n2).Thisalgorithmislessefficientonlargecollectionsthanotheralgorithms,suchasquick,heap,andmergesort.Inreallife,agoodexampleofinsertionsortisthewaycardsaremanuallysortedbytheplayers inagameofbridge.Theimplementationoftheinsertionsortalgorithmisshowninthefollowingcodesnippet.TheRandomSequencefunctiontakesthenumberofelementsasaparameterandreturnsanarrayofrandomintegers:

//mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingfmtandbytespackageimport("fmt""math/rand""time")

//randomSequencemethodfuncrandomSequence(numint)[]int{

varsequence[]intsequence=make([]int,num,num)rand.Seed(time.Now().UnixNano())variintfori=0;i<num;i++{sequence[i]=rand.Intn(999)-rand.Intn(999)}returnsequence}

Let'stakealookatthedifferentinsertionmethodsinthenextsections.

InsertionSortermethod

TheimplementationoftheInsertionSortermethodisshowninthefollowingsnippet.Thismethodtakesthearray of integersasaparameterandsortsthem:

//InsertionSortermethodfuncInsertionSorter(elements[]int){varn=len(elements)variint

fori=1;i<n;i++{varjintj=iforj>0{ifelements[j-1]>elements[j]{elements[j-1],elements[j]=elements[j],elements[j-1]}j=j-1}}}

Themainmethod

ThemainmethodinitializesthesequencebyinvokingtherandomSequencefunction,asshowninthefollowingcode.TheInsertionSorterfunctiontakesthesequenceandsortsitinascendingorder:

//mainmethodfuncmain(){

varsequence[]intsequence=randomSequence(24)fmt.Println("\n^^^^^^BeforeSorting^^^\n\n",sequence)InsertionSorter(sequence)fmt.Println("\n---AfterSorting---\n\n",sequence,"\n")}

Runthefollowingcommand toexecutetheinsertion_sort.gofile:goruninsertion_sort.go

Theoutputisasfollows:

Let'stakealookattheshellsort algorithminthenextsection.

ShellTheshellsortalgorithmsortsapairofelementsthatare notinsequence inacollection.Thedistancebetweentheelementstobecomparedisdecreasedsequentially.Thisalgorithmperformsmoreoperationsandhasagreater cachemissratiothanthequicksortalgorithm.Inthefollowingcode, wecanseetheimplementationofthe shellsort algorithm.TheShellSorterfunctiontakesanintegerarrayasaparameterandsortsit:

//mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingfmtandbytespackageimport("fmt")

//shellsortermethodfuncShellSorter(elements[]int){var(n=len(elements)intervals=[]int{1}k=1

)

for{varintervalintinterval=power(2,k)+1ifinterval>n-1{break}intervals=append([]int{interval},intervals...)k++}varintervalintfor_,interval=rangeintervals{variintfori=interval;i<n;i+=interval{varjintj=iforj>0{ifelements[j-interval]>elements[j]{elements[j-interval],elements[j]=elements[j],elements[j-interval]

interval]

}j=j-interval}}}}

Let'stakealookatthedifferentshellmethodsinthefollowingsections.

Thepowermethod

Thepowermethodtakesexponentandindexasparametersandreturnsthepoweroftheexponenttotheindex,asfollows:

//powerfunctionfuncpower(exponentint,indexint)int{varpowerintpower=1forindex>0{ifindex&1!=0{power*=exponent}index>>=1exponent*=exponent}returnpower}

Themainmethod

ThemainmethodinitializestheelementsintegerarrayandinvokestheShellSortermethod,asfollows:

//mainmethodfuncmain(){varelements[]intelements=[]int{34,202,13,19,6,5,1,43,506,12,20,28,17,100,25,4,5,97,1000,27}ShellSorter(elements)fmt.Println(elements)}

Runthefollowingcommand toexecutetheshell_sort.gofile:gorunshell_sort.go

Theoutputisasfollows:

Let'stakealookatthemergesort algorithminthenextsection.

MergeThemergesortalgorithmisacomparison-basedmethodthatwasinventedbyJohnVonNeumann.Eachelementintheadjacentlistiscomparedforsorting. TheperformanceofthealgorithmisintheorderofO(nlogn).Thisalgorithmisthebestalgorithmforsortingalinkedlist.Thefollowingcodesnippetdemonstratesthemergesortalgorithm. ThecreateArrayfunctiontakesnumintasaparameterandreturnsaninteger, array,thatconsistsofrandomizedelements:

//mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingfmtandbytespackageimport("fmt""math/rand""time")

//createarrayfunccreateArray(numint)[]int{vararray[]intarray=make([]int,num,num)rand.Seed(time.Now().UnixNano())variintfori=0;i<num;i++{array[i]=rand.Intn(99999)-rand.Intn(99999)}returnarray}

Let'stakealookatthedifferentmergemethodsinthefollowingsections.

MergeSortermethod

TheMergeSortermethodtakesanarrayofintegerelements asaparameter, andtwosub-arraysofelementsarerecursivelypassedtotheMergeSortermethod.Theresultantarraysarejoinedandreturnedasthecollection,asfollows:

//MergeSorteralgorithmfuncMergeSorter(array[]int)[]int{

iflen(array)<2{returnarray}varmiddleintmiddle=(len(array))/2returnJoinArrays(MergeSorter(array[:middle]),MergeSorter(array[middle:]))}

JoinArraysmethod

TheJoinArraysfunctiontakesthe leftArrandrightArrintegerarraysasparameters.Thecombinedarrayisreturnedinthefollowingcode:

//JoinArraysmethodfuncJoinArrays(leftArr[]int,rightArr[]int)[]int{

varnumintvariintvarjintnum,i,j=len(leftArr)+len(rightArr),0,0vararray[]intarray=make([]int,num,num)

varkintfork=0;k<num;k++{ifi>len(leftArr)-1&&j<=len(rightArr)-1{array[k]=rightArr[j]j++}elseifj>len(rightArr)-1&&i<=len(leftArr)-1{array[k]=leftArr[i]i++}elseifleftArr[i]<rightArr[j]{array[k]=leftArr[i]i++}else{array[k]=rightArr[j]j++}}returnarray}

Themainmethod

Themainmethodinitializestheintegerarrayof40elements,andtheelementsareprintedbeforeandaftersorting,asfollows:

//mainmethodfuncmain(){

varelements[]intelements=createArray(40)fmt.Println("\nBeforeSorting\n\n",elements)fmt.Println("\n-AfterSorting\n\n",MergeSorter(elements),"\n")}

Runthefollowingcommand toexecutethemerge_sort.gofile:gorunmerge_sort.go

Theoutputisasfollows:

Let'stakealookatthequicksort algorithminthefollowingsection.

QuickQuicksortisanalgorithmforsortingtheelementsofacollectioninanorganizedway. Parallelized quicksortistwotothreetimesfasterthanmergesortandheapsort.Thealgorithm'sperformanceisoftheorderO(nlogn). Thisalgorithmisaspace-optimizedversionofthebinarytreesortalgorithm.Inthefollowingcodesnippet,thequicksortalgorithmisimplemented.TheQuickSorterfunctiontakesanarrayofintegerelements,upperint,andbelowint asparameters.Thefunctiondividesthearrayintoparts,whicharerecursivelydividedandsorted:

//mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingfmtpackageimport("fmt")

//QuickSortermethodfuncQuickSorter(elements[]int,belowint,upperint){ifbelow<upper{varpartintpart=divideParts(elements,below,upper)QuickSorter(elements,below,part-1)QuickSorter(elements,part+1,upper)}}

Let'stakealookatthedifferentquickmethodsinthefollowingsections.

ThedividePartsmethod

ThedividePartsmethodtakesanarrayofintegerelements,upperint,andbelowint asparameters.Themethodsortstheelementsinascendingorder,asshowninthefollowingcode:

//dividePartsmethodfuncdivideParts(elements[]int,belowint,upperint)int{varcenterintcenter=elements[upper]variinti=belowvarjintforj=below;j<upper;j++{ifelements[j]<=center{swap(&elements[i],&elements[j])i+=1}}swap(&elements[i],&elements[upper])returni}

Theswapmethod

Inthefollowingcodesnippet,theswapmethodexchangeselementsbyinterchangingthevalues:

//swapmethodfuncswap(element1*int,element2*int){varvalintval=*element1*element1=*element2*element2=val}

Themainmethod

Themainmethodaskstheusertoinputthenumberofelementsandtheelementstoberead.Thearrayisinitializedandprintedbeforeandaftersorting,asfollows:

//mainmethodfuncmain(){varnumint

fmt.Print("EnterNumberofElements:")fmt.Scan(&num)

vararray=make([]int,num)

variintfori=0;i<num;i++{fmt.Print("array[",i,"]:")fmt.Scan(&array[i])}

fmt.Print("Elements:",array,"\n")QuickSorter(array,0,num-1)fmt.Print("SortedElements:",array,"\n")}

Runthefollowingcommandtoexecutethequick_sort.gofile:gorunquick_sort.go

Theoutputisasfollows:

Nowthatwearedonewithsortalgorithms,let'stakealookatthesearchalgorithmsinthenextsection.

Searching

Searchalgorithmsareusedtoretrieveinformationthat'sstoredinadatasourceoracollection.Thealgorithmisgiventhekeyoftheelementinquestion,and theassociatedvalue willbefound. SearchalgorithmsreturnatrueorafalseBooleanvaluebasedontheavailabilityoftheinformation.Theycanbeenhancedtodisplaymultiplevaluesrelatedtothesearchcriteria.Differenttypesofsearchalgorithmsincludelinear,binary,andinterpolation.Thesealgorithmsarecategorizedbythetypeofsearch.Searchalgorithmsincludebruteforceandheuristicmethods.Thealgorithmsarechosenfortheirefficiency.Differentfactorsforchoosingthesealgorithmsareasfollows:

InputtypeOutputtypeDefinitenessCorrectnessFinitenessEffectivenessGenerality

Inthissection,wewilldiscussthedifferenttypesofsearchalgorithms.

LinearThelinearsearchmethodfindsagivenvaluewithinacollectionbysequentially checkingeveryelementinthecollection.ThetimecomplexityofthelinearsearchalgorithmisO(n).Thebinarysearchalgorithmandhashtablesperformbetterthanthissearchalgorithm.Theimplementationofthelinearsearchmethodisshowninthefollowingcodesnippet.The LinearSearchfunctiontakesanarray of integerelementsandfindElementintasparameters.ThefunctionreturnsaBooleantrueifthefindElementisfound;otherwise,itreturnsfalse:

//mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingfmtpackageimport("fmt")

//LinearSearchmethodfuncLinearSearch(elements[]int,findElementint)bool{varelementintfor_,element=rangeelements{ifelement==findElement{returntrue}}returnfalse}

Themainmethodinitializesthearray of integerelementsandinvokestheLinearSearchmethodbypassinganintegerthatneedstobefound,asfollows:

//mainmethodfuncmain(){varelements[]intelements=[]int{15,48,26,18,41,86,29,51,20}fmt.Println(LinearSearch(elements,48))}

Runthefollowingcommandtoexecutethelinear_search.gofile:gorunlinear_search.go

Theoutputisasfollows:

Let'stakealookatthebinarysearch algorithminthefollowingsection.

BinaryThebinarysearchalgorithmcomparestheinputvaluetothemiddleelementofthesortedcollection.Ifthevaluesarenotequal,thehalfinwhichtheelementisnotfoundiseliminated.Thesearchcontinuesontheremaininghalfofthecollection.Thetimecomplexityofthisalgorithmisintheorderof O(logn).Thefollowingcodesnippetshowsanimplementationofthebinarysearchalgorithmusingthesort.Searchfunctionfromthesortpackage.Themainmethodinitializestheelementsarrayandinvokesthesort.Searchfunctiontofindanintegerelement:

//mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingfmtpackageimport("fmt""sort")

//mainmethodfuncmain(){varelements[]intelements=[]int{1,3,16,10,45,31,28,36,45,75}varelementintelement=36

variint

i=sort.Search(len(elements),func(iint)bool{returnelements[i]>=element})ifi<len(elements)&&elements[i]==element{fmt.Printf("foundelement%datindex%din%v\n",element,i,elements)}else{fmt.Printf("element%dnotfoundin%v\n",element,elements)}}

Runthefollowingcommandtoexecutethebinary_search.gofile:gorunbinary_search.go

Theoutputisasfollows:

Let'stakealookattheinterpolationsearch algorithminthefollowingsection.

Interpolation

Theinterpolationsearchalgorithmsearchesfortheelementinasortedcollection.Thealgorithmfindstheinputelementatanestimatedpositionbydiminishingthesearchspacebeforeoraftertheestimatedposition.ThetimecomplexityofthesearchalgorithmisoftheorderO(loglogn).Thefollowingcodesnippetimplementstheinterpolationsearchalgorithm.TheInterpolationSearchfunctiontakesthearrayofintegerelementsandtheintegerelementtobefoundasparameters.ThefunctionfindstheelementinthecollectionandreturnstheBooleanandtheindexforthefoundelement:

//mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingfmtpackageimport("fmt")

//interpolationsearchmethodfuncInterpolationSearch(elements[]int,elementint)(bool,int){varmidintvarlowintlow=0varhighinthigh=len(elements)-1

forelements[low]<element&&elements[high]>element{mid=low+((element-elements[low])*(high-low))/(elements[high]-elements[low])

ifelements[mid]<element{low=mid+1}elseifelements[mid]>element{high=mid-1}else{returntrue,mid}}

ifelements[low]==element{returntrue,low}elseifelements[high]==element{returntrue,high}else{

}else{

returnfalse,-1}

returnfalse,-1}

ThemainmethodinitializesthearrayofintegerelementsandinvokestheInterpolationSearchmethod withtheelementsarrayandtheelementparameters,asfollows:

//mainmethodfuncmain(){varelements[]intelements=[]int{2,3,5,7,9}varelementintelement=7varfoundboolvarindexintfound,index=InterpolationSearch(elements,element)fmt.Println(found,"foundat",index)}

Runthefollowingcommandtoexecutetheinterpolation_search.gofile:goruninterpolation_search.go

Theoutputisasfollows:

Nowthatwearedonewithsearchalgorithms,let'stakealookattherecursionalgorithmsinthenextsection.

Recursion

Recursionisanalgorithminwhichoneofthestepsinvokesthecurrentlyrunningmethodorfunction. Thisalgorithmacquirestheoutcomefortheinputbyapplyingbasictasksandthenreturnsthevalue.ThismethodwasbrieflydiscussedintheDivideandconqueralgorithmssectionofChapter1,DataStructuresandAlgorithms.Duringrecursion,ifthebaseconditionisnotreached,thenastackoverflowconditionmayarise.Arecursionalgorithmisimplementedinthefollowingcodesnippet.TheFactormethodtakesthenumasaparameterandreturnsthefactorialofnum.Themethodusesrecursiontocalculatethefactorialofthenumber:

//mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingfmtandbytespackageimport("fmt")

//factorialmethodfuncFactor(numint)int{ifnum<=1{return1}returnnum*Factor(num-1)}

Themainmethoddefinestheintegerwithavalueof 12 andinvokestheFactormethod.Thefactorialofthenumber12isprinted,asshowninthefollowingcode:

//mainmethodfuncmain(){varnumint=12fmt.Println("Factorial:%dis%d",num,Factor(num))}

Runthefollowingcommandtoexecutetherecurse_factorial.gofile:gorunrecurse_factorial.go

Theoutputisasfollows:

Nowthatwearedonewithrecursivealgorithms,let'stakealookatthehashalgorithmsinthenextsection.

Hashing

HashfunctionswereintroducedinChapter4,Non-LinearDataStructures. HashimplementationinGohascrc32andsha256implementations.AnimplementationofahashingalgorithmwithmultiplevaluesusinganXORtransformationisshowninthefollowingcodesnippet. TheCreateHashfunctiontakesabytearray, byteStr,asaparameterandreturnsthe sha256checksumofthebytearray:

//mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingfmtpackageimport("fmt""crypto/sha1""hash")

//CreateHashmethodfuncCreateHash(byteStr[]byte)[]byte{varhashValhash.HashhashVal=sha1.New()hashVal.Write(byteStr)

varbytes[]byte

bytes=hashVal.Sum(nil)returnbytes}

Inthefollowingsections,wewilldiscussthedifferentmethodsofhashalgorithms.

TheCreateHashMutliplemethod

TheCreateHashMutliplemethodtakesthebyteStr1andbyteStr2bytearraysasparametersandreturnstheXOR-transformedbytesvalue,asfollows:

//CreatehashforMultipleValuesmethodfuncCreateHashMultiple(byteStr1[]byte,byteStr2[]byte)[]byte{returnxor(CreateHash(byteStr1),CreateHash(byteStr2))}

The XORmethod

ThexormethodtakesthebyteStr1andbyteStr2bytearraysasparametersandreturnstheXOR-transformationresult,asfollows:

//XORmethodfuncxor(byteStr1[]byte,byteStr2[]byte)[]byte{varxorbytes[]bytexorbytes=make([]byte,len(byteStr1))variintfori=0;i<len(byteStr1);i++{xorbytes[i]=byteStr1[i]^byteStr2[i]}returnxorbytes}

Themainmethod

ThemainmethodinvokesthecreateHashMutliplemethod,passingCheck andHash as stringparameters,andprintsthehashvalueofthestrings,asfollows:

//mainmethodfuncmain(){

varbytes[]bytebytes=CreateHashMultiple([]byte("Check"),[]byte("Hash"))

fmt.Printf("%x\n",bytes)}

Runthefollowingcommandtoexecutethehash.gofile:gorunhash.go

Theoutputisasfollows:

SummaryThischaptercoveredsortingalgorithmssuchasbubble,selection,insertion,shell,merge,andquicksort.Searchalgorithmssuchaslinear,binary,andinterpolationwerethediscussed.Finally,therecursionandhashingalgorithmswereexplainedwithcodesnippets.Allofthealgorithmswerediscussedalongside codeexamplesandperformanceanalysis.Inthenextchapter,networkrepresentationusinggraphsandsparsematrixrepresentationusinglistoflistswillbe covered,alongwithappropriateexamples.

Questions1. Whatistheorderofcomplexityofbubblesort?2. Whichsortingalgorithmtakesoneelementatatimetocreateafinalsortedcollection?

3. Whatsortingmethodsortspairsofelementsthatarefarapartfromeachother?

4. Whatisthecomplexityofusingthemergesortalgorithm?5. Whichisbetter:thequick,merge,orheapsortalgorithm?6. Whatarethedifferenttypesofsearchalgorithms?7. Provideacodeexampleoftherecursionalgorithm.8. Whowasthefirstpersontodescribetheinterpolationsearch?9. Whichsortingalgorithmisbasedonacomparison-basedmethodofanadjacentlistofelements?

10. Whowasthepersontopublishtheshellsortalgorithm?

Furtherreading

Thefollowingbooksarerecommendedifyouwanttoknowmoreaboutalgorithmssuchassorting,selecting,searching,andhashing:

DesignPatterns, byErichGamma,RichardHelm,RalphJohnson,andJohnVlissidesIntroductiontoAlgorithms –ThirdEdition,byThomasH.Cormen,CharlesE.Leiserson,RonaldL.Rivest,andCliffordSteinDatastructuresandAlgorithms:AnEasyIntroduction,by RudolphRussell

Section3:AdvancedDataStructuresandAlgorithmsusingGo

Networkrepresentation,sparsematrixrepresentation,memorymanagement,instancebasedlearning,compilertranslation,andprocessscheduling-relateddatastructuresandalgorithmsarepresentedinthissection.Thedatastructuresshowninthealgorithmsaregraphs,listoflists,AVLtrees,K-Dtrees,balltrees,VanEmdeBoastrees,buffertrees,andred-blacktrees.Cache-obliviousdatastructuresanddataflowanalysisarecoveredwithcodeexamplesandefficiencyanalysis.Thissectioncontainsthefollowingchapters:

Chapter9, NetworkandSparseMatrixRepresentationChapter10, MemoryManagement

NetworkandSparseMatrixRepresentation

Asparsematrixisamatrixinwhichmostofthevaluesarezero.Theratioofzerovaluestonon-zerovaluesisknownasthesparsity.Anestimationofamatrix'ssparsitycanbehelpfulwhencreatinghypothesesabouttheavailabilityofnetworks.Extensivebigsparsematricesarecommonlyusedinmachinelearningandnaturallanguageparsing.Itiscomputationallycostlytoworkwiththem.Recommendationenginesusethemforrepresenting productsinsideacatalog.Computervisionuses sparsematricesandnetworkdatastructures whenworkingwithpicturesthatcontainsectionswithdarkpixels.Networkandsparsematrixdatastructuresarealsousedinsocialgraphsandmaplayouts.Inthischapter,wewillcoverthefollowingtopics:

Networkrepresentationsusinggraphs:SocialnetworkrepresentationMaplayoutsKnowledgegraphs

Sparsematrixrepresentationusingalistoflists

Asocialgraphthatconnectspeopleisimplemented inthischapter, andacodeexampleshowshowthegraphcanbetraversed.Maplayoutsareexplainedwithgeographiclocationswithlatitudeandlongitude.Knowledgegraphsareexplainedviatheuseofacaranditsparts.

TechnicalrequirementsInstallGoversion1.10fromhttps://golang.org/doc/installforyourOS.TheGitHubURLforthecodeinthischapterisasfollows: https://github.com/PacktPublishing/Learn-Data-Structures-and-Algorithms-with-Golang/tree/master/Chapter09.

NetworkrepresentationusinggraphsAgraphisarepresentationofasetofobjectsthat'sconnectedbylinks.Thelinksconnectvertices,whicharepoints.Thebasicoperationsonagrapharetheadditionandremovaloflinksandvertices.Thesearesomedifferenttypesofgraphs:

DirectedgraphNon-directedgraphConnectedgraphNon-connectedgraphSimplegraphMulti-graph

Anadjacencylistconsistsofadjacentverticesofagraphthathaveobjectsorrecords.Anadjacencymatrixconsistsofsourceanddestinationvertices.Anincidencematrixisatwo-dimensionalBooleanmatrix.Thematrixhasrowsofverticesandcolumnsthatrepresentthelinks(edges).Networkrepresentationusingagraph isshowninthefollowingcode.Asocialgraphconsistsofanarrayoflinks:

///mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingfmtpackageimport("fmt")//SocialGraphtypeSocialGraphstruct{SizeintLinks[][]Link}

TheLinkstructisdefinedandimplementedinthenextsection.

TheLinkclassTheLinkclassconsistsofthevertex1andvertex2vertices andtheLinkWeightintegerproperty:

//LinkclasstypeLinkstruct{Vertex1intVertex2intLinkWeightint}

Thenextsectiontalksaboutthe implementationofthedifferentLinkclassmethods.

TheNewSocialGraphmethod

TheNewSocialGraphfunctioncreatesasocialgraphgivennum,whichisthesizeofthegraph.Sizeisthenumberoflinksinthegraph:

//NewSocialGraphmethodfuncNewSocialGraph(numint)*SocialGraph{return&SocialGraph{Size:num,Links:make([][]Link,num),}}

TheAddLinkmethod

TheAddLinkmethodaddsthelinkbetweentwovertices.The AddLinkmethodofasocialgraphtakesvertex1,vertex2,andweightasparameters.Themethodaddsthelinkfromvertex1tovertex2,asshowninthefollowingcode:

//AddLinkmethodfunc(socialGraph*SocialGraph)AddLink(vertex1int,vertex2int,weightint){socialGraph.Links[vertex1]=append(socialGraph.Links[vertex1],Link{Vertex1:vertex1,Vertex2:vertex2,LinkWeight:weight})}

ThePrintLinksmethod

ThePrintLinksmethodoftheSocialGraphclassprintsthelinksfromvertex=0andallthelinksinthegraph:

//PrintLinksExamplefunc(socialGraph*SocialGraph)PrintLinks(){

varvertexintvertex=0

fmt.Printf("Printingalllinksfrom%d\n",vertex)varlinkLinkfor_,link=rangesocialGraph.Links[vertex]{fmt.Printf("Link:%d->%d(%d)\n",link.Vertex1,link.Vertex2,link.LinkWeight)}

fmt.Println("Printingalllinksingraph.")varadjacent[]Linkfor_,adjacent=rangesocialGraph.Links{for_,link=rangeadjacent{fmt.Printf("Link:%d->%d(%d)\n",link.Vertex1,link.Vertex2,link.LinkWeight)}}}

Themainmethod

ThemainmethodcreatesasocialgraphbyinvokingtheNewSocialGraphmethod.Thelinksfrom0to1,0to2,1to3,and2to4areaddedtothesocialgraph.ThelinksareprintedusingtheprintLinksmethod:

//mainmethodfuncmain(){

varsocialGraph*SocialGraph

socialGraph=NewSocialGraph(4)

socialGraph.AddLink(0,1,1)socialGraph.AddLink(0,2,1)socialGraph.AddLink(1,3,1)socialGraph.AddLink(2,4,1)

socialGraph.PrintLinks()

}

Runthefollowingcommandtoexecutethesocial_graph.gofile:gorunsocial_graph.go

Theoutputisasfollows:

Inthenextsection,wewilltakealookattheunittestforthesocialgraph

Inthenextsection,wewilltakealookattheunittestforthesocialgraph

method.

TestHere,wehavewrittenaunittestforthesocialgraphmethod.Thecodeisasfollows:

///mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingtestingpackageimport("fmt""testing")//NewSocialGraphtestmethodfuncTestNewSocialGraph(test*testing.T){

varsocialGraph*SocialGraph

socialGraph=NewSocialGraph(1)

ifsocialGraph==nil{

test.Errorf("errorincreatingasocialGraph")}

}

Runthefollowingcommandtoexecutetheprecedingcodesnippet:gotest-runNewSocialGraph-v

Theoutputisasfollows:

Inthenextsection, asocialnetworkrepresentation willbeimplementedwithcodeexamples.Theprecedinggraphwillbeenhancedwithnodes.Eachnodewillrepresentasocialentity.

RepresentingasocialnetworkAsocialnetworkconsistsofsociallinksthatcontainsocialentitiessuchaspeople,friends,discussions,shares,beliefs,trust,andlikes.Thisgraphisusedtorepresentthesocialnetwork.Metrics relatedtotheproximityofentities canbecalculatedbasedonthegraph. Socialgraphsconsistofgraphnodesandlinks,whicharemapswithakeynameandmultiplekeysnames,respectively:

///Mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingfmtpackageimport("fmt")

typeNamestring

typeSocialGraphstruct{GraphNodesmap[Name]struct{}Linksmap[Name]map[Name]struct{}}

Thedifferentsocialnetworkmethodsareexplainedandimplementedinthenextsection.

TheNewSocialGraphmethod

The NewSocialGraph methodreturnsasocialgraphconsistingof nil-valuedGraphNodesandLinks:

//NewSocialGraphmethodfuncNewSocialGraph()*SocialGraph{return&SocialGraph{GraphNodes:make(map[Name]struct{}),Links:make(map[Name]map[Name]struct{}),}}

TheAddEntitymethod

TheAddEntitymethodaddstheentitytothesocialgraph.The AddEntitymethodofthe SocialGraphclasstakesnameasaparameterandreturnstrueifitisaddedtothesocialgraph:

//AddEntitymethodfunc(socialGraph*SocialGraph)AddEntity(nameName)bool{

varexistsboolif_,exists=socialGraph.GraphNodes[name];exists{returntrue}socialGraph.GraphNodes[name]=struct{}{}returntrue}

TheAddLinkmethod

TheAddLinkmethodoftheSocialGraphclasstakesname1andname2 as parameters.Thismethodcreatestheentitiesifthenamedentitiesdonotexistandcreatesalinkbetweentheentities:

//AddLinkfunc(socialGraph*SocialGraph)AddLink(name1Name,name2Name){varexistsboolif_,exists=socialGraph.GraphNodes[name1];!exists{socialGraph.AddEntity(name1)}if_,exists=socialGraph.GraphNodes[name2];!exists{socialGraph.AddEntity(name2)}if_,exists=socialGraph.Links[name1];!exists{socialGraph.Links[name1]=make(map[Name]struct{})}socialGraph.Links[name1][name2]=struct{}{}}

ThePrintLinksmethod

ThePrintLinksmethodoftheSocialGraphclassprintsthelinksadjacenttotheroot andallthelinks,asshowninthefollowingcodesnippet:

func(socialGraph*SocialGraph)PrintLinks(){varrootNameroot=Name("Root")

fmt.Printf("Printingalllinksadjacentto%d\n",root)

varnodeNamefornode=rangesocialGraph.Links[root]{//Edgeexistsfromutov.fmt.Printf("Link:%d->%d\n",root,node)}

varmmap[Name]struct{}fmt.Println("Printingalllinks.")forroot,m=rangesocialGraph.Links{varvertexNameforvertex=rangem{//Edgeexistsfromutov.fmt.Printf("Link:%d->%d\n",root,vertex)}}}

Themainmethod

Themainmethodcreatesasocialgraph.Theentities,suchasjohn,per,andcynthia,arecreatedandlinkedwiththerootnode.Thefriends,suchasmayo,lorrie,andellie,arecreatedandlinkedwithjohnandper:

//mainmethodfuncmain(){

varsocialGraph*SocialGraph

socialGraph=NewSocialGraph()

varrootName=Name("Root")varjohnName=Name("JohnSmith")varperName=Name("PerJambeck")varcynthiaName=Name("CynthiaGibas")

socialGraph.AddEntity(root)socialGraph.AddEntity(john)socialGraph.AddEntity(per)socialGraph.AddEntity(cynthia)

socialGraph.AddLink(root,john)socialGraph.AddLink(root,per)socialGraph.AddLink(root,cynthia)

varmayoName=Name("MayoSmith")varlorrieName=Name("LorrieJambeck")varellieName=Name("EllieVlocksen")

socialGraph.AddLink(john,mayo)socialGraph.AddLink(john,lorrie)socialGraph.AddLink(per,ellie)

socialGraph.PrintLinks()}

Runthefollowingcommandtoexecutethesocial_graph_example.gofile:gorunsocial_graph_example.go

Theoutputisasfollows:

Thenextsectiontalksaboutthemaplayoutimplementation.

MaplayoutsAmaplayoutisageographicalvisualizationoflocationsthatarelinkedtogether.Thenodesinthegraphofamapconsistofgeo-basedinformation.Thenodewillhaveinformationsuchasthenameofthelocation,latitude,andlongitude.Mapsarelaidoutindifferentscales.Cartographicdesignisreferredtoasmapcreationusinggeographicinformation.Amaplayoutisshowninthefollowingcodesnippet.ThePlaceclassconsistsofName,Latitude,andLongitudeproperties:

///mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingfmtpackageimport("fmt")

//PlaceclasstypePlacestruct{

NamestringLatitudefloat64Longitudefloat64

}

ThenextsectiontalksabouttheMapLayout class.

TheMapLayoutclassTheMapLayoutclassconsistsofGraphNodesandLinks:

//MapLayoutclasstypeMapLayoutstruct{GraphNodesmap[Place]struct{}Linksmap[Place]map[Place]struct{}}

ThedifferentMapLayoutmethodsareexplainedandimplementedinthenextsection.

TheNewMapLayoutmethod

TheNewMapLayoutmethodcreatesaMapLayout.TheMapLayouthasGraphNodesandlinksmaps:

//NewMapLayoutmethodfuncNewMapLayout()*MapLayout{return&MapLayout{GraphNodes:make(map[Place]struct{}),Links:make(map[Place]map[Place]struct{}),}}

TheAddPlacemethod

TheAddPlacemethodoftheMapLayoutclasstakesplace asa parameterandreturnstrueiftheplaceexists.Iftheplacedoesnotexist,thenagraphnodewithanewplacekeyiscreated:

//AddPlacemethodfunc(mapLayout*MapLayout)AddPlace(placePlace)bool{

varexistsboolif_,exists=mapLayout.GraphNodes[place];exists{returntrue}mapLayout.GraphNodes[place]=struct{}{}returntrue}

TheAddLinkmethod

TheAddLinkmethodoftheMapLayoutclasstakestheplacesasparametersandlinksthemtogether:

//AddLinkfunc(mapLayout*MapLayout)AddLink(place1Place,place2Place){varexistsboolif_,exists=mapLayout.GraphNodes[place1];!exists{mapLayout.AddPlace(place1)}if_,exists=mapLayout.GraphNodes[place2];!exists{mapLayout.AddPlace(place2)}

if_,exists=mapLayout.Links[place1];!exists{mapLayout.Links[place1]=make(map[Place]struct{})}mapLayout.Links[place1][place2]=struct{}{}

}

 ThePrintLinksmethod

ThePrintLinksmethodofMapLayoutprintstheplacesandthelinks://PrintLinksmethodfunc(mapLayout*MapLayout)PrintLinks(){varrootPlaceroot=Place{"Algeria",3,28}

fmt.Printf("Printingalllinksadjacentto%s\n",root.Name)

varnodePlacefornode=rangemapLayout.Links[root]{fmt.Printf("Link:%s->%s\n",root.Name,node.Name)}

varmmap[Place]struct{}fmt.Println("Printingalllinks.")forroot,m=rangemapLayout.Links{varvertexPlaceforvertex=rangem{fmt.Printf("Link:%s->%s\n",root.Name,vertex.Name)}}}

Themainmethod

Inthemainmethod,themaplayoutiscreatedbyinvokingtheNewMapLayoutmethod.Placesareinstantiatedandaddedtothemaplayout.Then,thelinksareaddedbetweenplaces:

//mainmethodfuncmain(){

varmapLayout*MapLayout

mapLayout=NewMapLayout()

varrootPlace=Place{"Algeria",3,28}varnetherlandsPlace=Place{"Netherlands",5.75,52.5}

varkoreaPlace=Place{"Korea",124.1,-8.36}vartunisiaPlace=Place{"Tunisia",9,34}

mapLayout.AddPlace(root)mapLayout.AddPlace(netherlands)mapLayout.AddPlace(korea)mapLayout.AddPlace(tunisia)

mapLayout.AddLink(root,netherlands)mapLayout.AddLink(root,korea)mapLayout.AddLink(root,tunisia)

varsingaporePlace=Place{"Singapore",103.8,1.36}varuaePlace=Place{"UAE",54,24}varjapanPlace=Place{"Japan",139.75,35.68}

mapLayout.AddLink(korea,singapore)mapLayout.AddLink(korea,japan)mapLayout.AddLink(netherlands,uae)

mapLayout.PrintLinks()}

Runthefollowingcommandtoexecutethemap_layout.gofile:gorunmap_layout.go

Theoutputisasfollows:

Inthenextsection,wewilltakealookattheunittestfortheNewMapLayoutmethod.

TestAunittestfortheMapLayoutclass'sNewMapLayoutmethod isshowninthefollowingcodesnippet:

///mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingtestingpackageimport("testing")

//NewMapLayouttestmethodfuncTestNewMapLayout(test*testing.T){

varmapLayout*MapLayout

mapLayout=NewMapLayout()

test.Log(mapLayout)

ifmapLayout==nil{

test.Errorf("errorincreatingamapLayout")}

}

Runthefollowingcommandtoexecutetheprecedingcodesnippet:gotest-runNewMapLayout-v

Theoutputisasfollows:

Thenextsectiontalksaboutimplementinga knowledgegraph.

KnowledgegraphsAknowledgegraphisanetworkrepresentationofentities,items,andusersasnodes.Thenodesinteractwithoneanothervialinksoredges.Knowledgegraphsarewidelyusedbecausetheyareschemaless.Thesedatastructuresareusedtorepresentknowledgeintheformofgraphs,andthenodeshavetextualinformation.Knowledgegraphsarecreatedbyusingitem,entity,andusernodesandlinkingthemwithedges.Anontologyconsistsofaknowledgegraphofinformationnodes.Thereasonerderivesknowledgefromknowledgegraphs.Aknowledgegraphconsistsofclasses,slots,andfacets,whichareontologicalterms. Inthefollowingcode,aknowledgegraphconsistingofacar'sbillofmaterialsisexplained.The Class typeconsistsofaname,whichisastring:

///mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingfmtpackageimport("fmt")

//ClassTypetypeClassstruct{Namestring}

Thenextsectiontalksabouttheknowledgegraph class.

TheKnowledgeGraphclassTheKnowledgeGraphclassconsistsofGraphNodesandlinks:

//KnowledgeGraphtypetypeKnowledgeGraphstruct{GraphNodesmap[Class]struct{}Linksmap[Class]map[Class]struct{}}

Thedifferentknowledgegraphmethodsareexplainedandimplementedinthefollowingsections.

TheNewKnowledgeGraphmethod

TheNewKnowledgeGraphmethodcreatesaknowledgegraph,whichconsistsofGraphNodesandLinksmaps:

//NewKnowledgeGraphmethodfuncNewKnowledgeGraph()*KnowledgeGraph{return&KnowledgeGraph{GraphNodes:make(map[Class]struct{}),Links:make(map[Class]map[Class]struct{}),}}

TheAddClassmethod

TheAddClassmethodoftheKnowledgeGraphclasstakesclassasaparameter andreturnstrueiftheclassexists.Iftheclassdoesnotexist,aGraphNodeiscreatedwithclassasakey:

//AddClassmethodfunc(knowledgeGraph*KnowledgeGraph)AddClass(classClass)bool{

varexistsboolif_,exists=knowledgeGraph.GraphNodes[class];exists{returntrue}knowledgeGraph.GraphNodes[class]=struct{}{}returntrue}

TheAddLinkmethod

TheAddLinkmethodoftheKnowledgeGraphclasstakesclass1andclass2 as parameters,andalinkiscreatedbetweentheseclasses:

//AddLinkfunc(knowledgeGraph*KnowledgeGraph)AddLink(class1Class,class2Class){varexistsboolif_,exists=knowledgeGraph.GraphNodes[class1];!exists{knowledgeGraph.AddClass(class1)}if_,exists=knowledgeGraph.GraphNodes[class2];!exists{knowledgeGraph.AddClass(class2)}

if_,exists=knowledgeGraph.Links[class1];!exists{knowledgeGraph.Links[class1]=make(map[Class]struct{})}knowledgeGraph.Links[class1][class2]=struct{}{}

}

ThePrintLinksmethod

ThePrintLinksmethodoftheKnowledgeGraphclassprintsthelinksandnodes:

//PrintLinksmethodfunc(knowledgeGraph*KnowledgeGraph)PrintLinks(){varcarClasscar=Class{"Car"}

fmt.Printf("Printingalllinksadjacentto%s\n",car.Name)

varnodeClassfornode=rangeknowledgeGraph.Links[car]{fmt.Printf("Link:%s->%s\n",car.Name,node.Name)}

varmmap[Class]struct{}fmt.Println("Printingalllinks.")forcar,m=rangeknowledgeGraph.Links{varvertexClassforvertex=rangem{fmt.Printf("Link:%s->%s\n",car.Name,vertex.Name)}}}

Themainmethod

Themainmethodcreatestheknowledgegraph,andtheclassesareinstantiated.Thelinksbetweentheclassesarecreatedandprinted:

//mainmethodfuncmain(){

varknowledgeGraph*KnowledgeGraph

knowledgeGraph=NewKnowledgeGraph()

varcar=Class{"Car"}vartyre=Class{"Tyre"}vardoor=Class{"Door"}varhood=Class{"Hood"}

knowledgeGraph.AddClass(car)knowledgeGraph.AddClass(tyre)knowledgeGraph.AddClass(door)knowledgeGraph.AddClass(hood)

knowledgeGraph.AddLink(car,tyre)knowledgeGraph.AddLink(car,door)knowledgeGraph.AddLink(car,hood)

vartube=Class{"Tube"}varaxle=Class{"Axle"}varhandle=Class{"Handle"}varwindowGlass=Class{"WindowGlass"}

knowledgeGraph.AddClass(tube)knowledgeGraph.AddClass(axle)knowledgeGraph.AddClass(handle)knowledgeGraph.AddClass(windowGlass)

knowledgeGraph.AddLink(tyre,tube)knowledgeGraph.AddLink(tyre,axle)knowledgeGraph.AddLink(door,handle)knowledgeGraph.AddLink(door,windowGlass)

knowledgeGraph.PrintLinks()}

Runthefollowingcommandtoexecutethe knowledge_catalog.gofile:

gorunknowledge_catalog.go

Theoutputisasfollows:

Inthenextsection,wewilltakealookattheunittestfortheNewKnowledgeGraphmethod.

TestTheNewKnowledgeGraphmethodisunittestedinthefollowingcodesnippet:

///mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingtestingpackageimport("testing")

//NewKnowledgeGraphtestmethodfuncTestNewKnowledgeGraph(test*testing.T){

varknowledgeGraph*KnowledgeGraph

knowledgeGraph=NewKnowledgeGraph()

test.Log(knowledgeGraph)

ifknowledgeGraph==nil{

test.Errorf("errorincreatingaknowledgeGraph")}

}

Runthefollowingcommandtoexecutetheprecedingcodesnippet:gotest-runNewKnowledgeGraph-v

Theoutputisasfollows:

Thenextsectiontalksabouttherepresentationofthe sparsematrix.

SparsematrixrepresentationusingalistoflistsAsparsematrixisatwo-dimensionallistofmrowsandncolumns.Theshapeofamatrixismxnifitconsistsofmrowsandncolumns.Sparsematricesareusedforsolvinglarge-scaleproblemsthatdonotrequiredensematrices.Forexample,partialdifferentialequationsaresolvedbyusingthe finiteelementmethod(FEM).Tuplesofasparsematrixarenon-zeroelementsofthematrix.Inthefollowingcode,asparsematrixismodeledasalistoflists.Asparsematrixconsistsofcellsthatarealistoflists.EachcellhaspropertiessuchasRow,Column,andValue:

///mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingfmtpackageimport("fmt")

//ListofListtypeLOLstruct{RowintColumnintValuefloat64}

ThenextsectiontalksabouttheSparseMatrixclass.

SparseMatrixclassSparseMatrixhasacellsarrayandshape,whichisanintegerarray:

//SparseMatrixtypeSparseMatrixstruct{cells[]LOLshape[2]int}

Inthenextsection,thedifferentSparsemethodsofthe SparseMatrixstructareimplemented.

TheShapemethod

TheShapemethodoftheSparseMatrixclassreturnstheshapearrayelements:

//Shapemethodfunc(sparseMatrix*SparseMatrix)Shape()(int,int){returnsparseMatrix.shape[0],sparseMatrix.shape[1]}

TheNumNonZeromethod

TheNumNonZeromethodfindsthecellswithnon-zeroelements.The NumNonZeromethodoftheSparseMatrixclassreturnsthesizeofthecellsarrayinsparseMatrix:

//NumNonZeromethodfunc(sparseMatrix*SparseMatrix)NumNonZero()int{returnlen(sparseMatrix.cells)}

TheLessThanmethod

TheLessThanmethodcomparesthelistoflistsrowsandcolumnsandcheckswhethertherowislessthaniandthatthecolumnislessthanj:

//LessThanmethodfuncLessThan(lolLOL,iint,jint)bool{

iflol.Row<i&&lol.Column<j{

returntrue}

returnfalse}

TheEqualmethod

TheEqualmethodcheckswhetherthelistoflistsrowsandcolumnsareequaltoiandj,respectively:

//EqualmethodfuncEqual(lolLOL,iint,jint)bool{iflol.Row==i&&lol.Column==j{returntrue}returnfalse}

TheGetValuemethod

TheGetValuemethodoftheSparseMatrixclassreturnsthevalueofthecellwhoserowandcolumnequaliandj,respectively:

//GetValuemethodfunc(sparseMatrix*SparseMatrix)GetValue(iint,jint)float64{varlolLOLfor_,lol=rangesparseMatrix.cells{ifLessThan(lol,i,j){continue}ifEqual(lol,i,j){returnlol.Value}return0.0}return0.0}

TheSetValuemethod

TheSetValuemethodoftheSparseMatrixclasssetsthevalueofthecellwiththerowandcolumnequaltoiandj,respectively,astheparametervalue:

//SetValuemethodfunc(sparseMatrix*SparseMatrix)SetValue(iint,jint,valuefloat64){

varlolLOLvarindexintforindex,lol=rangesparseMatrix.cells{ifLessThan(lol,i,j){continue}ifEqual(lol,i,j){sparseMatrix.cells[index].Value=valuereturn}

sparseMatrix.cells=append(sparseMatrix.cells,LOL{})varkintfork=len(sparseMatrix.cells)-2;k>=index;k--{sparseMatrix.cells[k+1]=sparseMatrix.cells[k]}sparseMatrix.cells[index]=LOL{Row:i,Column:j,Value:value,}return}sparseMatrix.cells=append(sparseMatrix.cells,LOL{Row:i,Column:j,Value:value,})}

TheNewSparseMatrixmethod

TheNewSparseMatrixmethodtakesthemandnasparameters andreturnstheinitializedmatrix:

//NewSparseMatrixmethodfuncNewSparseMatrix(mint,nint)*SparseMatrix{return&SparseMatrix{cells:[]LOL{},shape:[2]int{m,n},}}

Themainmethod

ThemainmethodcreatesthesparsematrixbyinvokingtheNewSparseMatrixmethod.Thevaluesaresetincells(1,1)and(1,3).Thesparsematrixandthenumberofnon-zerocellsareprinted:

//mainmethodfuncmain(){

varsparseMatrix*SparseMatrix

sparseMatrix=NewSparseMatrix(3,3)

sparseMatrix.SetValue(1,1,2.0)sparseMatrix.SetValue(1,3,3.0)

fmt.Println(sparseMatrix)fmt.Println(sparseMatrix.NumNonZero())}

Runthefollowingcommandtoexecutethesparse_matrix.gofile:gorunsparse_matrix.go

Theoutputisasfollows:

SummaryThischaptercoveredhowtopresentnetworksandsparsematricesusinggraphsandalistoflists,respectively. Socialnetworkrepresentation,maplayouts,andknowledgegraphswerediscussedindetailwithcodeexamples.Thedifferentsparsematrixmethodswerealsoimplementedwiththeappropriatecode.Inthenextchapter,algorithmssuchasgarbagecollection,cachemanagement,andspaceallocationwillbepresentedwithcodeexamplesandanefficiencyanalysis.

QuestionsWhatdatastructureisusedtorepresentasetoflinkedobjects?Whatisatwo-dimensionalmatrixwithBooleanvaluescalled?Giveacodeexampleforanetworkrepresentationusingagraph.Whichmetricscanbecalculatedfromasocialgraph?Whatisacartographicdesign?Giveanexampleofaknowledgegraphanddefinetheclass,slots,andfacets.Whataretheapplicationsofsparsematrices?Definealistoflistsandwriteacodesample.Whatisamaplayout?Whatdifferentoperationscanbeperformedusinggraphs?

Furtherreading

Thefollowingbooksarerecommendedifyouwanttoknowmoreaboutgraphsandlistoflists:

DesignPatterns, byErichGamma,RichardHelm,RalphJohnson,andJohnVlissidesIntroductiontoAlgorithms –ThirdEdition,byThomasH.Cormen,CharlesE.Leiserson,RonaldL.Rivest,andCliffordSteinDatastructuresandAlgorithms:AnEasyIntroduction,by RudolphRussell

MemoryManagementMemorymanagementisawaytocontrolandorganizememory.Memorydivisionsarecalledblocks,andtheyareusedforrunning differentprocesses.Thebasicgoalofmemorymanagementalgorithmsistodynamicallydesignatesegmentsofmemorytoprogramsondemand.Thealgorithmsfreeupmemoryforreusewhentheobjectsinthememoryareneverrequiredagain.Garbagecollection,cachemanagement,andspaceallocationalgorithmsaregoodexamplesofmemorymanagementtechniques.Insoftwareengineering,garbagecollectionisusedtofreeupmemorythat'sbeenallocatedtothoseobjectsthatwon'tbeusedagain,thushelpinginmemorymanagement. Thecacheprovidesin-memorystoragefordata.Youcansortthedatainthecacheintolocale-specificgroups.Thedatacanbestoredusingkeyandvaluesets.Thischaptercoversthegarbagecollection,cachemanagement,andspaceallocationalgorithms.Thememorymanagementalgorithmsarepresentedwithcodesamplesandefficiencyanalyses.Thefollowingtopicswillbecoveredinthischapter:

GarbagecollectionCachemanagementSpaceallocationConcepts—Gomemorymanagement

We'lllookatgarbagecollectionfirst,thenlookatthedifferentalgorithmsrelatedtogarbagecollection.

TechnicalrequirementsInstallGoVersion1.10fromGolang(https://golang.org/),choosingtherightversionforyourOS.TheGitHubrepositoryforthecodeinthischaptercanbefoundhere: https://github.com/PacktPublishing/Learn-Data-Structures-and-Algorithms-with-Golang/tree/master/Chapter10.

Garbagecollection

Garbagecollectionisatypeofprogrammedmemorymanagementinwhichmemory,currentlyoccupiedbyobjectsthatwillneverbeusedagain,isgathered.JohnMcCarthywasthefirstpersontocomeupwithgarbagecollectionformanagingLispmemorymanagement.Thistechniquespecifieswhichobjectsneedtobede-allocated,andthendischargesthememory.Thestrategiesthatareutilizedforgarbagecollectionarestackallocationandregioninterference.Sockets,relationaldatabasehandles,userwindowobjects,andfileresourcesarenotoverseenbygarbagecollectors.Garbagecollectionalgorithmshelpreducedanglingpointerdefects,double-freedefects,andmemoryleaks.Thesealgorithmsarecomputing-intensiveandcausedecreasedorunevenperformance.AccordingtoApple,oneofthereasonsforiOSnothavinggarbagecollectionisthatgarbagecollectionneedsfivetimesthememorytomatchexplicitmemorymanagement.Inhigh-transactionalsystems,concurrent,incremental,andreal-timegarbagecollectorshelpmanagememorycollectionandrelease.Garbagecollectionalgorithmsdependonvariousfactors:

GCthroughputHeapoverheadPausetimesPausefrequencyPausedistributionAllocationperformanceCompactionConcurrencyScalingTuningWarm-uptimePagereleasePortabilityCompatibility

That'ssimple,deferred,one-bit,weightedreferencecounting,mark-and-sweep,andgenerationalcollectionalgorithmsdiscussedinthefollowingsections.

TheReferenceCounterclassThefollowingcodesnippetshowshowreferencestocreated objectsaremaintainedinthestack.TheReferenceCounterclasshasthenumberofreferences,includingthepoolofreferencesandremovedreferences,asproperties:

//mainpackagehasexamplesshown//inHands-OnDataStructuresandalgorithmswithGobookpackagemain

//importingfmtpackageimport("fmt""sync")

//ReferenceCountertypeReferenceCounterstruct{num*uint32pool*sync.Poolremoved*uint32}

Let'stakealookatthemethodoftheReferenceCounterclass.

ThenewReferenceCountermethod

ThenewReferenceCountermethodinitializesaReferenceCounterinstanceandreturnsapointertoReferenceCounter.Thisisshowninthefollowingcode:

//newReferenceCountermethodfuncnewReferenceCounter()*ReferenceCounter{return&ReferenceCounter{num:new(uint32),pool:&sync.Pool{},removed:new(uint32),}}

TheStackclassisdescribedinthenextsection.

TheStackclassTheStackclassconsistsofareferencesarrayandCountasproperties.Thisisshowninthefollowingcode:

//StackclasstypeStackstruct{references[]*ReferenceCounterCountint}

Let'stakealookatthemethodsofthe Stackclass.

TheStackclass–anewmethod

Now,let'slookattheheapinterfacemethodsthatareimplementedbytheStackclass.Thenewmethodinitializesthereferencesarray,andthe PushandPop heapinterfacemethodstakethereferenceparameter topushandpopreferenceoutofthestack.Thisisshowninthefollowingcode:

//NewmethodofStackClassfunc(stack*Stack)New(){stack.references=make([]*ReferenceCounter,0)}

//Pushmethodfunc(stack*Stack)Push(reference*ReferenceCounter){stack.references=append(stack.references[:stack.Count],reference)stack.Count=stack.Count+1}

//Popmethodfunc(stack*Stack)Pop()*ReferenceCounter{ifstack.Count==0{returnnil}varlengthint=len(stack.references)varreference*ReferenceCounter=stack.references[length-1]iflength>1{stack.references=stack.references[:length-1]}else{stack.references=stack.references[0:]}stack.Count=len(stack.references)returnreference}

Themainmethod

Inthefollowingcodesnippet,let'sseehowStackisused.AStack instanceisinitialized,andreferencesareaddedtothestackbyinvokingthePushmethod.ThePopmethodisinvokedandtheoutputisprinted:

//mainmethodfuncmain(){varstack*Stack=&Stack{}stack.New()varreference1*ReferenceCounter=newReferenceCounter()varreference2*ReferenceCounter=newReferenceCounter()varreference3*ReferenceCounter=newReferenceCounter()varreference4*ReferenceCounter=newReferenceCounter()stack.Push(reference1)stack.Push(reference2)stack.Push(reference3)stack.Push(reference4)fmt.Println(stack.Pop(),stack.Pop(),stack.Pop(),stack.Pop())}

Runthefollowingcommandstoexecutethestack_garbage_collection.gofile:

gorunstack_garbage_collection.go

Theoutputisasfollows:

Thereferencecounting,mark-and-sweep,andgenerationalcollectionalgorithmswillbediscussedinthefollowingsections.

Referencecounting

Referencecountingisatechniquethat'susedforkeepingthecountofreferences,pointers,andhandlestoresources.Memoryblocks,diskspace,andobjectsaregoodexamplesofresources.Thistechniquetrackseachobjectasaresource.Themetricsthataretrackedarethenumberofreferencesheldbydifferentobjects.Theobjectsarerecoveredwhentheycanneverbereferenced again.Thenumberofreferencesisusedforruntimeoptimizations.Deutsch-Bobrowcameupwiththestrategyofreferencecounting.Thisstrategywasrelatedtothenumberofupdatedreferencesthatwereproducedbyreferencesthatwereputinlocalvariables.HenryBakercameupwithamethodthatincludesreferencesinlocalvariablesthataredeferreduntilneeded.Inthefollowingsubsections,thesimple,deferred,one-bit,andweightedtechniquesofreferencecountingwillbediscussed.

Simplereferencecounting

Referencecountingisrelatedto keepingthenumberofreferences,pointers,andhandlestoaresourcesuchasanobject,blockofmemory,ordiskspace.Thistechniqueisrelatedtothenumberofreferencestode-allocatedobjectsthatareneverreferencedagain.Thecollectiontechniquetracks,foreachobject,atallyofthenumberofreferencestotheobject. Thereferencesareheldbyotherobjects.Theobjectgetsremovedwhenthenumberofreferences totheobjectiszero.Theremovedobjectbecomesinaccessible. Theremovalof areferencecanpromptcountlessconnectedreferencestobepurged. Thealgorithmistime-consumingbecauseofthesizeoftheobjectgraphandslowaccessspeed. Inthefollowingcodesnippets,wecanseeasimplereference-countingalgorithmbeingimplemented.The ReferenceCounterclasshasnumber(num),pool,andremovedreferencesasproperties:

///mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingsync,atomicandfmtpackagesimport("sync/atomic""sync""fmt")

//ReferenceCountertypeReferenceCounterstruct{num*uint32pool*sync.Poolremoved*uint32}

ThenewReferenceCounter,Add,andSubtractmethodsoftheReferenceCounterclassareshowninthefollowingsnippet:

//newReferenceCountermethodfuncnewReferenceCounter()ReferenceCounter{returnReferenceCounter{num:new(uint32),pool:&sync.Pool{},removed:new(uint32),}}

//Addmethodfunc(referenceCounterReferenceCounter)Add(){atomic.AddUint32(referenceCounter.num,1)}

//Subtractmethodfunc(referenceCounterReferenceCounter)Subtract(){ifatomic.AddUint32(referenceCounter.num,^uint32(0))==0{atomic.AddUint32(referenceCounter.removed,1)}}

Let'slookatthemainmethodandseeanexampleofsimplereferencecounting.ThenewReferenceCountermethodisinvoked,andareferenceisaddedbyinvokingtheAddmethod.Thecount referenceisprintedattheend.Thisisshowninthefollowingcodesnippet

//mainmethodfuncmain(){varreferenceCounterReferenceCounterreferenceCounter=newReferenceCounter()referenceCounter.Add()fmt.Println(*referenceCounter.count)}

Runthefollowingcommandstoexecutethereference_counting.gofile:gorunreference_counting.go

Theoutputisasfollows:

Thedifferenttypesofreferencecountingtechniquesaredescribedinthefollowingsections.

Deferredreferencecounting

Deferredreferencecountingisaprocedure inwhichreferencesfromdifferentobjectstoagivenobjectarecheckedandprogram-variablereferencesareoverlooked. Ifthetallyofthereferencesiszero,thatobjectwillnotbeconsidered.Thisalgorithmhelpsreducetheoverheadofkeepingcounts uptodate.Deferredreferencecountingissupportedbymanycompilers.

One-bitreferencecounting

Theone-bitreferencecountingtechnique utilizesasolitarybitflagtoshowwhetheranobjecthasoneormorereferences. Theflagisstoredaspartoftheobjectpointer.Thereisnorequirement tospareanyobjectforextraspaceinthistechnique.Thistechniqueisviablesince themajorityofobjectshaveareferencecountof1.

Weightedreferencecounting

Theweightedreferencecountingtechnique talliesthenumberofreferencestoanobject,andeachreferenceisdelegatedaweight.Thistechniquetracksthetotalweightofthereferencestoanobject. WeightedreferencecountingwasinventedbyBevan,Watson,andWatsonin1987.Thefollowingcodesnippetshowsanimplementationoftheweightedreferencecountingtechnique:

//ReferenceCountertypeReferenceCounterstruct{num*uint32pool*sync.Poolremoved*uint32weightint}

//WeightedReferencemethodfuncWeightedReference()int{varreferences[]ReferenceCounterreferences=GetReferences(root)varreferenceReferenceCountervarsumintfor_,reference=rangereferences{sum=sum+reference.weight}returnsum}

Themark-and-sweepalgorithm

Themark-and-sweepalgorithmisbasedonanideathatwasproposedbyDijkstrain1978.Inthegarbagecollectionstyle,theheapconsistsofagraphofconnectedobjects,whicharewhite.Thistechniquevisitstheobjectsandcheckswhether theyarespecificallyavailablebytheapplication. Globalsandobjectsonthestackareshadedgrayinthistechnique.Everygrayobjectisdarkenedtoblackandfilteredforpointerstootherobjects. Anywhiteobjectfoundintheoutputisturnedgray.Thiscalculationisrehasheduntiltherearenograyobjects.Whiteobjectsthatareleftoutareinaccessible.Amutatorinthisalgorithmhandlesconcurrencybychangingthepointerswhilethecollectorisrunning.Italsotakescareoftheconditionsothatnoblackobjectpointstoawhiteobject.Themarkalgorithmhasthefollowingsteps:

1. Marktherootobject2. Marktherootbitastrueifthevalueofthebit isfalse3. Foreveryreferenceofroot,markthereference,asinthefirststep

Thefollowingcodesnippetshowsthemarkingalgorithm.Let'slookattheimplementationoftheMark method:

funcMark(root*object){varmarkedAlreadyboolmarkedAlready=IfMarked(root)if!markedAlready{map[root]=true}varreferences*object[]references=GetReferences(root)varreference*objectfor_,reference=rangereferences{Mark(reference)}}

Thesweepalgorithm'spseudocodeispresentedhere:Foreachobjectintheheap,markthebitasfalseifthevalueofthebitistrueIfthevalueofthebitistrue,releasetheobjectfromtheheap

Thesweepalgorithmreleasestheobjectsthataremarkedforgarbagecollection.Now,let'slookattheimplementationofthe sweepalgorithm: 

funcSweep(){varobjects*[]object

varobjects*[]object

objects=GetObjects()varobject*objectfor_,object=rangeobjects{varmarkedAlreadyboolmarkedAlready=IfMarked(object)ifmarkedAlready{map[object]=true}Release(object)}}

Thegenerationalcollectionalgorithm

Thegenerationalcollectionalgorithmdividestheheapofobjectsintogenerations.Agenerationofobjectswillbeexpiredandcollectedbythealgorithmbasedontheirage.Thealgorithmpromotesobjectstooldergenerationsbasedontheageoftheobjectinthegarbagecollectioncycle.Theentireheapneedstobescavenged,evenifagenerationiscollected.Let'ssaygeneration3iscollected;inthiscase,generations0-2arealsoscavenged.Thegenerationalcollectionalgorithmispresentedinthefollowingcodesnippet:

funcGenerationCollect(){varcurrentGenerationintcurrentGeneration=3varobjects*[]objectobjects=GetObjectsFromOldGeneration(3)varobject*objectfor_,object=rangeobjects{varmarkedAlreadyboolmarkedAlready=IfMarked(object)ifmarkedAlready{map[object]=true}}}

We'lltakealookatcachemanagementinthenextsection.

CachemanagementCachemanagementconsistsofmanagingstatic,dynamic,andvariableinformation:

StaticinformationneverchangesDynamicinformationchangesfrequentlyVariableinformationchangeslessfrequentlythandynamicinformation

Theobjectcacheisstoredinvariousdatastructures,suchasmapsandtrees.Mapshaveakeyasanidentifierandavalue,whichisanobject.Cacheobjectscanberelatedtomemory,disks,pools,andstreams.Cacheshaveattributesrelatedtotimetolive,group,andregion.Aregionconsistsofacollectionofmappedkey-values.Regionscanbeindependentofotherregions.Cacheconfigurationconsistsofdefaults,regions,andauxiliaries.Atypicalcachemanagerhasthefollowingfeatures:

MemorymanagementThreadpoolcontrolsGroupingofelementsConfigurableruntimeparametersRegiondataseparationandconfigurationRemotesynchronizationRemotestorerecoveryEventhandlingRemoteserverchainingandfailoverCustomeventloggingCustomeventqueueinjectionKeypattern-matchingretrievalNetwork-efficientmulti-keyretrieval

The CacheObjectclassandthe Cacheclassaredescribedinthefollowingsections.

TheCacheObjectclassTheCacheObjectclasshasValueandTimeToLiveproperties.Thisisshowninthefollowingcode:

///mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingfmt,syncandtimepackagesimport("fmt""sync""time")

//CacheObjectclasstypeCacheObjectstruct{ValuestringTimeToLiveint64}

TheIfExpiredmethodoftheCacheObjectclassisshowninthenextsection.

TheIfExpiredmethod

IfExpiredcheckswhetherthecacheobjecthasexpired.The IfExpiredmethodofCacheObjectreturnstrueifTimeToLivehasnotexpired;otherwise,itreturnsfalse.Thisisshowninthefollowingcode:

//IfExpiredmethodfunc(cacheObjectCacheObject)IfExpired()bool{ifcacheObject.TimeToLive==0{returnfalse}returntime.Now().UnixNano()>cacheObject.TimeToLive}

TheCacheclassTheCacheclassconsistsof objectsmapwitha string key,aCacheObjectvalue, andasync.RWMutexmutex.Thisisshowninthefollowingcode:

//CacheclasstypeCachestruct{objectsmap[string]CacheObjectmutex*sync.RWMutex}

TheNewCache,GetObject,and SetValuemethodsoftheCacheclassareshowninthefollowingsections.

TheNewCachemethod

TheNewCachemethodreturnsapointertoacache,whichisinitializedwiththe nilmap(thatis,amapwithoutvalues) andRWMutex.Thisisshowninthefollowingcode:

//NewCachemethodfuncNewCache()*Cache{return&Cache{objects:make(map[string]CacheObject),mutex:&sync.RWMutex{},}}

TheGetObjectmethod

TheGetObject methodretrievestheobjectgiventhecachekey.The GetObjectmethodoftheCacheclassreturnsthevalueofcacheKey.TheRLockmethodonthemutexobjectofthecacheisinvoked,andtheRUnlockmethodisdeferredbeforereturningthevalueofcacheKey.Iftheobjecthasexpired,thekeyvaluewillbeanemptystring.Thisisshowninthefollowingcode:

//GetObjectmethodfunc(cacheCache)GetObject(cacheKeystring)string{cache.mutex.RLock()defercache.mutex.RUnlock()varobjectCacheObjectobject=cache.objects[cacheKey]ifobject.IfExpired(){delete(cache.objects,cacheKey)return""}returnobject.Value}

TheSetValuemethod

TheSetValuemethodoftheCacheclasstakescacheKey,cacheValue,andtimeToLiveparameters.TheLockmethod onthemutexobjectofthecacheisinvoked,andtheUnlockmethodisdeferred.AnewCacheObjectiscreatedwithcacheValueandTimeToLiveasproperties.ThecreatedcacheObjectissetasavaluetomapobjectswiththecacheKeykey.Thisisshowninthefollowingcode:

//SetValuemethodfunc(cacheCache)SetValue(cacheKeystring,cacheValuestring,timeToLivetime.Duration){cache.mutex.Lock()defercache.mutex.Unlock()cache.objects[cacheKey]=CacheObject{Value:cacheValue,TimeToLive:time.Now().Add(timeToLive).UnixNano(),}}

We'llimplementthemethodswejusttookalookatinthemainmethodinthenextsection.

Themainmethod

ThemainmethodcreatesthecachebyinvokingtheNewCachemethod.ThekeyandvaluearesetonthecachebyinvokingsetValue.ThevalueisaccessedbycallingtheGetObjectmethodoftheCacheclass.Thisisshowninthefollowingcode:

//mainmethodfuncmain(){varcache*Cachecache=NewCache()cache.SetValue("name","johnsmith",200000000)varnamestringname=cache.GetObject("name")fmt.Println(name)}

Runthefollowingcommandtoexecutethecache_management.gofile:goruncache_management.go

Theoutputisasfollows:

Thenextsectiontalksaboutthespaceallocationalgorithm.

Spaceallocation

Eachfunctionhasstackframesassociatedwithindividualmemoryspace.Functionshaveaccesstothememory insidetheframe,andaframepointerpointstothememory'slocation.Transitionbetweenframesoccurswhenthefunctionisinvoked.Dataistransferredbyvaluefromoneframetoanotherduringthetransition.Stackframecreationandmemoryallocationisdemonstratedinthefollowingcode.The addOne functiontakesnumandincrementsitbyone.Thefunctionprintsthevalueandaddressofnum:

///mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingfmtpackageimport("fmt")

//incrementmethodfuncaddOne(numint){num++fmt.Println("addedtonum",num,"Addressofnum",&num)}

Themainmethodinitializesthevariablenumberas17.ThenumbervalueandaddressareprintedbeforeandafterinvokingtheaddOnefunction.Thisisshowninthefollowingcode:

//mainmethodfuncmain(){varnumberintnumber=17fmt.Println("valueofnumber",number,"Addressofnumber",&number)addOne(number)fmt.Println("valueofnumberafteraddingOne",number,"Addressof",&number)}

Runthefollowingcommandtoexecutethestack_memory_allocation.gofile:gorunstack_memory_allocation.go

Theoutputisasfollows:

Framepointersareexplainedinthenextsection.

PointersPointershaveanaddressthatis4or8byteslong,dependingonwhetheryouhavea32-bitor64-bitarchitecture.Thestack'smainframeconsistsofthenumber17withtheaddress0xc420016058.Afteraddingone,anewframewithnumequalto18andanaddressof0xc420016068iscreated.Themainmethodprintsthestack'smainframeafterinvokingtheaddOnefunction. Thecodeinthefollowingsectionsdemonstratesmemoryspaceallocationwithpointersinsteadofactualvaluespassedintoafunction.TheAddOneandmainmethodsofpointersareshowninthefollowingsections.

TheaddOnemethod

The addOne functiontakesapointertonumandincrementsitby1.Thefunctionprintsthevalue,address,andpointerofnum.Thisisshowninthefollowingcode:

///mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingfmtpackageimport("fmt")

//incrementmethodfuncaddOne(num*int){*num++fmt.Println("addedtonum",num,"Addressofnum",&num,"ValuePointsTo",*num)}

Themainmethod

Themainmethodinitializesthevariablenumberto17.ThepointertothenumberispassedtotheaddOnefunction.ThenumbervalueandaddressisprintedbeforeandafterinvokingtheaddOnefunction.Inthisexample,theaddressofthenumberisthesameasthe value of numintheaddOnefunction.Pointerssharetheaddressofthevariableforthefunctiontoaccessforreadsandwriteswithinthestackframe.Pointertypesarespecifictoeverytypethatisdeclared.Pointersprovideindirectmemoryaccessoutsidethefunction'sstackframe.Thisisshowninthefollowingcode:

//mainmethodfuncmain(){varnumberintnumber=17fmt.Println("valueofnumber",number,"Addressofnumber",&number)addOne(&number)fmt.Println("valueofnumberafteraddingOne",number,"Addressof",&number)}

Runthefollowingcommandtoexecutethestack_memory_pointer.gofile:gorunstack_memory_pointer.go

Theoutputisasfollows:

ThenextsectiontalksaboutmemorymanagementinGo.

Concepts– GomemorymanagementInGo,programmersdon'tneedtoworryaboutcodingavariable'svalueplacementinmemoryandspaceallocation.GarbagecollectioninGoisoverseenbythememorymanager.TheGOGC variableisusedtosetavaluefortheinitialgarbagecollectiontargetpercentage.Garbagecollectionisactivatedwhentheproportionoffreshlyallotteddatatothelivedatathat remainsafterthepreviousgarbagecollection reachesthetargetpercentage.Thedefaultvalueofthe GOGCvariable is100.Thissettingcanbeturnedoff,whichstopsgarbagecollection. ThecurrentimplementationofgarbagecollectioninGousesthemark-and-sweepalgorithm.Someofthebestpracticesthatyoucanfollowtoimprovememorymanagementareasfollows:

SmallobjectscanbecombinedintolargerobjectsLocalvariablesthathaveescapedfromtheirdeclarationscopecanbepromotedintoheapallocationsSlicearraypre-allocationcanbeperformedtoimprovememoryUseint8,insteadofint,because int8isasmallerdatatypeObjectsthatdonothaveanypointerswillnotbescannedbythegarbagecollectorFreeListscanbeusedtoreusetransientobjectsandreducethenumberofallocations

Profiling

ProfilinginGocanbeenabledbyusingthecpuprofile andmemprofileflags.TheGotestingpackagehassupportforbenchmarkingandprofiling.Thecpuprofileflagcanbeinvokedbythefollowingcommand:

gotest-run=none-bench=ClientServerParallel4-cpuprofile=cprofilenet/http

Thebenchmarkcanbewrittentoacprofileoutputfileusingthefollowingcommand:

gotoolpprof--texthttp.testcprof

Let'slookatanexampleofhowtoprofiletheprogramsthatyouhavewritten.Theflag.Parsemethodreadsthecommand-lineflags. TheCPUprofilingoutputiswrittentoafile.TheStopCPUProfilemethodontheprofileriscalledtoflushanypendingfileoutputthatneedstobewrittenbeforetheprogramstops:

varprofile=flag.String("cpuprofile","","cpuprofiletooutputfile")funcmain(){flag.Parse()if*profile!=""{varfile*os.Filevarerrerrorfile,err=os.Create(*profile)iferr!=nil{log.Fatal(err)}pprof.StartCPUProfile(file)deferpprof.StopCPUProfile()}

SummaryThischaptercoveredthegarbagecollection,cachemanagement,andmemoryspaceallocationalgorithms.Welookedatreferencecountingalgorithms,includingsimple,deferred,one-bit,andweighted.Themark-and-sweepandgenerationalcollectionalgorithmswerealsopresentedwithcodeexamples. Thenextchapterwillcoverthenextstepswecantakeaftergoingthroughthisbook.

Questions1. Whichfactorsareconsideredwhenchoosingagarbagecollectionalgorithm?

2. Inwhichreferencecountingalgorithmareprogram-variablereferencesignored?

3. Whatisthetypeofreferencecountingalgorithminwhichasingle-bitflagisusedforcounting?

4. Inwhichreferencecountingalgorithmisaweightassignedtoeachreference?

5. Whoinventedweightedreferencecounting?6. WhichgarbagecollectionalgorithmwasproposedbyDijkstra?7. Whatclasshandlesconcurrencywhenthemark-and-sweepcollectorisrunning?

8. Whatarethecriteriaforpromotingobjectstooldergenerations?9. Drawaflowchartforthecachemanagementalgorithm.10. Howdoyougetindirectmemoryaccessoutsideamethod'sstack

frame?

Furtherreading

Thefollowingbooksarerecommendedifyouwanttoknowmoreaboutgarbagecollection:

DesignPatterns, byErichGamma,RichardHelm,RalphJohnson,andJohnVlissidesIntroductiontoAlgorithms –ThirdEdition,byThomasH.Cormen,CharlesE.Leiserson,RonaldL.Rivest,andCliffordSteinDatastructuresandAlgorithms:AnEasyIntroduction,by RudolphRussell

NextStepsInthisappendix,wesharethereader'slearningoutcomesfromthisbook.Thecoderepositorylinksandkeytakeawaysarepresented.Referencesareincludedforthelatestdatastructuresandalgorithms.Tipsandtechniquesareprovidedtohelpyoukeepyourselfuptodatewiththelatestondatastructuresandalgorithms.

TechnicalrequirementsInstallGoversion1.10fromhttps://golang.org/doc/install,beingsuretochoosethecorrectversionforyouroperatingsystem.TheGitHubrepositoryforthecodeinthisappendixcanbefoundhere: https://github.com/PacktPublishing/Learn-Data-Structures-and-Algorithms-with-Golang/tree/master/Appendix.

LearningoutcomesThelearningoutcomesfromthisbookareasfollows:

Improveawebormobile application'sperformanceusingthecorrectdatastructuresandalgorithms.Understandhowanalgorithmsolvesaproblemandhowthecorrectdatastructureischosenforaproblem.Enumeratethevarioussolutionstoaproblemandidentifyalgorithmsanddatastructuresafterdoingacost/benefit analysis.Getagraspofthevarioustechniquesforwritingpseudocodeforanalgorithm,allowingyouto acewhite-boardingsessionsandinterviewassignments.Discoverthepitfallsinselectingdatastructuresandalgorithmsbypredictinghowfastandefficientanalgorithmordatastructureis.

Inthefollowingsection,thekeytakeawaypoints,papers,andarticlestobereferredto,alongwithtipsandtechniques,arediscussed.

KeytakeawaysThekeytakeawaysforthereaderareasfollows:

Howtochoosethecorrectalgorithmanddatastructuresforaproblem.Howtocomparethecomplexityanddatastructuresofdifferent algorithms forcodeperformanceandefficiency.Howtoapplybestpracticestoimproveandincreasetheperformanceofanapplication.Real-worldproblems,solutions,andbestpracticesassociatedwithwebandmobilesoftwaresolutionsareprovidedinthebookascodeexamples.

NextstepsInthissection,papersandarticlesareprovidedasfurtherreadingforeachchapter.

Chapter1–DataStructuresandAlgorithmsThefollowingarticlesarerelatedtodatastructuresandalgorithms:

ThecompleteguidetoGoDataStructures(https://flaviocopes.com/golang-data-structures/)DataStructureandAlgorithms(http://www.golangprograms.com/data-structure-and-algorithms.html)DatastructuresinGo:Stacksandqueues(https://ieftimov.com/golang-datastructures-stacks-queues)

Thefollowingpapersarerelatedtodatastructuresandalgorithms:THEREPRESENTATIONOFALGORITHMS – DTIC(https://apps.dtic.mil/dtic/tr/fulltext/u2/697026.pdf)ONTHECOMPUTATIONALCOMPLEXITYOFALGORITHMS(https://fi.ort.edu.uy/innovaportal/file/20124/1/60-hartmanis_stearns_complexity_of_algorithms.pdf)AnalysisandPerformanceofDivideandConquerMethodology(http://ijarcet.org/wp-content/uploads/IJARCET-VOL-6-ISSUE-8-1295-1298.pdf)

Chapter2–GettingStartedwithGoforDataStructures and AlgorithmsThefollowingarticlesarerelatedtothecontentinthischapter:

Go–Datastructures (https://golanglibs.com/category/data-structures)Applied–GoAlgorithmsandDataStructures(https://appliedgo.net/domains/algorithms-and-data-structures/)EffectiveGo(https://golang.org/doc/effective_go.html)

Chapter3–LinearDataStructuresThefollowingarticlesarerelatedtolineardatastructures:

DataStructuresforBeginners:Arrays,HashMaps,andLists(https://adrianmejia.com/blog/2018/04/28/data-structures-time-complexity-for-beginners-arrays-hashmaps-linked-lists-stacks-queues-tutorial/)Stack-ArrayImplementation(https://www.cs.bu.edu/teaching/c/stack/array/)

Thefollowingpapersarerelatedtolineardatastructures:Linear-SpaceDataStructuresforRangeModeQueryinArrays (https://cs.au.dk/~larsen/papers/linear_mode.pdf)RESEARCHPAPERONSTACKANDQUEUE(http://www.ijirt.org/master/publishedpaper/IJIRT101357_PAPER.pdf)LinearDataStructuresforFastRay-ShootingamidstConvexPolyhedra(http://www.cs.tau.ac.il/~haimk/papers/ray.pdf)

Chapter4–Non-LinearDataStructuresThefollowingarticlesarerelatedtonon-lineardatastructures:

Overviewofnon-lineardatastructures(https://medium.com/@ankitkulhari/overview-of-non-linear-data-structures-40cb441f6d7)Non-linearDataStructures(http://euler.vcsu.edu:7000/9647/)WhatIsForestDataStructure?(https://magoosh.com/data-science/what-is-forest-data-structure/)TreeDataStructure(http://www.cs.cmu.edu/~clo/www/CMU/DataStructures/Lessons/lesson4_1.htm)

Thefollowingpapersarerelatedtonon-lineardatastructures:Y-Trees:Anextendingnon-lineardatastructureforbetterorganizationoflarge-sizeddata(https://ieeexplore.ieee.org/document/8234528)AShapeAnalysisforNon-linearDataStructures(https://link.springer.com/chapter/10.1007/978-3-642-15769-1_13)RepresentationofNonlinearDataSurfaces(https://www.semanticscholar.org/paper/Representation-of-Nonlinear-Data-Surfaces-Olsen-Fukunaga/f4f4812532ba427658ecc83d772637c076780acf)

Chapter5–HomogeneousDataStructuresThefollowingarticlesarerelatedtohomogeneousdatastructures:

USINGMATRICESINGO(LANG)(http://connor-johnson.com/2014/06/21/using-matrices-in-golang/)Golang:Linearalgebraandmatrixcalculationexample(https://www.socketloop.com/tutorials/golang-linear-algebra-and-matrix-calculation-example)GonumTutorial:LinearAlgebrainGo(https://medium.com/wireless-registry-engineering/gonum-tutorial-linear-algebra-in-go-21ef136fc2d7)MatrixMultiplicationinGolang(3x3matrices)(https://repl.it/@hygull/Matrix-multiplication-in-Golang2-matrices-of-order-3x3)

Chapter6–HeterogeneousDataStructuresThefollowingarticlesarerelatedto heterogeneousdatastructures:

HeterogeneousArrays(https://gist.github.com/cslarsen/5256744)OL(OrderedList)(https://www.w3.org/MarkUp/html3/seqlists.html)LargeOrderedLists(https://www.aerospike.com/docs/guide/llist.html)ImplementinganOrderedList(https://bradfieldcs.com/algos/lists/implementing-an-ordered-list/)

Chapter7–Dynamic DataStructuresThefollowingarticlesarerelatedtodynamicdatastructures:

ThecompleteguidetoGoDataStructures(https://flaviocopes.com/golang-data-structures/)DATASTRUCTUREANDALGORITHMS(http://www.golangprograms.com/data-structure-and-algorithms.html)DatastructuresinGo:Stacksandqueues(https://ieftimov.com/golang-datastructures-stacks-queues)

Thefollowingpapersarerelatedtodynamicdatastructures:THEREPRESENTATIONOFALGORITHMS – DTIC(https://apps.dtic.mil/dtic/tr/fulltext/u2/697026.pdf)ONTHECOMPUTATIONALCOMPLEXITYOFALGORITHMS(https://fi.ort.edu.uy/innovaportal/file/20124/1/60-hartmanis_stearns_complexity_of_algorithms.pdf)AnalysisandPerformanceofDivideandConquerMethodology(http://ijarcet.org/wp-content/uploads/IJARCET-VOL-6-ISSUE-8-1295-1298.pdf)

Chapter8– ClassicAlgorithmsThefollowingarticlesarerelatedtoclassicalgorithms:

SortingAlgorithmsPrimer(https://hackernoon.com/sorting-algorithms-primer-374b83f3ba09)Depth-FirstSearch(https://medium.com/@g789872001darren/gogoalgorithm-1-depth-first-search-582eeb58f23a)HashinginGo(GolangvsPython)(https://medium.com/@vworri/hashing-in-go-golang-vs-python-b7bc1194e967)IterativevsRecursivevsTail-RecursiveinGolang(https://medium.com/@felipedutratine/iterative-vs-recursive-vs-tail-recursive-in-golang-c196ca5fd489)

Thefollowingpapersarerelatedtoclassicalgorithms:AMathematicalModelingofPure,RecursiveAlgorithms(https://www.researchgate.net/publication/220810107_A_Mathematical_Modeling_of_Pure_Recursive_Algorithms)RecursivealgorithmsforestimationofhiddenMarkovmodelsandautoregressivemodelswithMarkovregime(https://ieeexplore.ieee.org/document/979322)Recursivealgorithmsforapproximatingprobabilitiesingraphicalmodels(https://papers.nips.cc/paper/1316-recursive-algorithms-for-approximating-probabilities-in-graphical-models.pdf)

Chapter9–NetworkandSparseMatrixRepresentation

Thefollowingarticlesarerelatedtonetworkandsparsematrixrepresentation:

EquationsAreGraphs(http://gopherdata.io/post/deeplearning_in_go_part_1/)FromTheoryToPractice:RepresentingGraphs(https://medium.com/basecs/from-theory-to-practice-representing-graphs-cfd782c5be38)GoDataStructures:Graph(https://flaviocopes.com/golang-data-structure-graph/)

Thefollowingpapersarerelatedtonetworkandsparsematrixrepresentation:

RepresentationLearningonGraphs:MethodsandApplications(https://www-cs.stanford.edu/people/jure/pubs/graphrepresentation-ieee17.pdf)Anoverviewonnetworkdiagrams:Graph-basedrepresentation(https://www.researchgate.net/publication/308049492_An_overview_on_network_diagrams_Graph-based_representation)Designprinciplesfororigin-destinationflowmaps(https://pdfs.semanticscholar.org/587a/730b11a4b3878142bd4995f80dc969bc5982.pdf)

InChapter9,NetworkandSparseMatrixRepresentation,usecasesfromreal-lifeapplicationswerepresented. Learninghowthenetworkdatastructureandsparsematrices areappliedindifferentdomains,suchasairlines,banking,medical,pharma,telecoms,andsupplychains,isagoodnextstepforthereader.

Chapter10–MemoryManagementThefollowingarticlesarerelatedtomemorymanagement:

GettingtoGo:TheJourneyofGo'sGarbageCollector(https://blog.golang.org/ismmkeynote)Moderngarbagecollection(https://blog.plan99.net/modern-garbage-collection-911ef4f8bd8e)GoLang:MemoryManagementandGarbageCollection(https://vikash1976.wordpress.com/2017/03/26/go-lang-memory-management-and-garbage-collection/)

Thefollowingpapersarerelatedtomemorymanagement:AnalysisoftheGoruntimescheduler(http://www.cs.columbia.edu/~aho/cs6998/reports/12-12-11_DeshpandeSponslerWeiss_GO.pdf)SimpleGenerationalGarbageCollectionandFastAllocation(http://www.cs.ucsb.edu/~ckrintz/racelab/gc/papers/appel88simplegen.pdf)ATime-andSpaceEfficientGarbageCompactionAlgorithm(http://www.cs.ucsb.edu/~ckrintz/racelab/gc/papers/morris-compaction.pdf)

ThedifferenttipsandtrickstobeusedinGodatastructuresandalgorithmarediscussedinthenextsection.

TipsandtechniquesTokeepupdatedonGo,youcansubscribetotheseforumsandblogs:

Gopherize:https://gopherize.me/?fromhttp=trueGolangWeekly: https://golangweekly.com/issues/240 TheGopherConference:https://www.gophercon.com/ GoogleGroups: https://groups.google.com/forum/m/#!newtopic/golang-dev SlackGroups:https://techbeacon.com/46-slack-groups-developers StackOverflow:http://stackoverflow.com/questions/tagged/go DaveCheney'sResourcesforNewGoProgrammers: https://dave.cheney.net/resources-for-new-go-programmers 

ThefollowingsectioncontainstipsforwritinggoodcodeinGo.

UsingchannelwithatimeoutintervalThesoftwareprogramthatconnectstoresourcescanbesetwithtimeouts.Channelsareusedforimplementingtimeouts.Youcanconfigureachannelwithatimeoutintervalasfollows:

//mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingerrors,logandtimepackagesimport("errors""log""time")

//delayTimeOutmethodfuncdelayTimeOut(channelchaninterface{},timeOuttime.Duration)(interface{},error){log.Printf("delayTimeOutenter")deferlog.Printf("delayTimeOutexit")vardatainterface{}select{case<-time.After(timeOut):returnnil,errors.New("delayTimeOuttimeout")casedata=<-channel:returndata,nil}}

//mainmethodfuncmain(){channel:=make(chaninterface{})gofunc(){varerrerrorvardatainterface{}data,err=delayTimeOut(channel,time.Second)iferr!=nil{log.Printf("error%v",err)return}log.Printf("data%v",data)}()channel<-struct{}{}time.Sleep(time.Second*2)gofunc(){varerrerrorvardatainterface{}data,err=delayTimeOut(channel,time.Second)iferr!=nil{

iferr!=nil{

log.Printf("error%v",err)return}log.Printf("data%v",data)}()time.Sleep(time.Second*2)}

Runthefollowingcommandtoexecutetheprecedingcodesnippet:gorunchan_timeout.go

Theoutputisasfollows:

UsingcontextinsteadofchannelContextscanbeimplementedinfunctionsexecutedinGoroutines.Contextsareusedinsteadofchannelinthecodeforpassinginformationbetweenprocesses.Thefollowingcodesnippetshowstheusageofcontext:

//mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingerrors,context,logandtimepackages

import("errors""golang.org/x/net/context""log""time")

//mainmethodfuncmain(){

vardelaytime.Duration

delay=time.Millisecond

varcancelcontext.CancelFunc

varcontexcontext.Context

contex,cancel=context.WithTimeout(context.Background(),delay)

gofunc(context.Context){<-contex.Done()log.Printf("contexdone")}(contex)

_=cancel

time.Sleep(delay*2)

log.Printf("contexend%v",contex.Err())

channel:=make(chanstruct{})

varerrerrorgofunc(chanstruct{}){select{case<-time.After(delay):err=errors.New("chdelay")case<-channel:}log.Printf("channeldone")}(channel)

time.Sleep(delay*2)

log.Printf("channelend%v",err)}

Runthefollowingcommand toexecutetheprecedingcodesnippet:goruncontext.go

Theoutputisasfollows:

Panic,defer,andrecoverPanic,defer,andrecoverareusedtohandlecomplexerrors.Thelastreturnedvariableinafunctionisusedasanerror.Thefollowingcodesnippetisanexampleofthis:

//mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingfmtanderrorspackages

import("fmt""errors"

)

//FirstFuncmethodfuncFirstFunc(vinterface{})(interface{},error){varokbool

if!ok{returnnil,errors.New("falseerror")}returnv,nil}

//SecondFuncmethodfuncSecondFunc(){deferfunc(){varerrinterface{}iferr=recover();err!=nil{fmt.Println("recoveringerror",err)}}()varvinterface{}v=struct{}{}varerrerrorif_,err=FirstFunc(v);err!=nil{panic(err)}

fmt.Println("Theerrorneverhappen")}

//mainmethodfuncmain(){SecondFunc()fmt.Println("Theexecutionended")}

Runthefollowingcommandtoexecutetheprecedingcodesnippet:gorunhandling_error.go

Theoutputisasfollows:

ThefollowinglinkcontainsomeusefultipsandtechniquesforwritingGocode: https://golang.org/doc/effective_go.html.

LoggingwiththelinenumberWhilelogging,youcanlogwiththelinenumberandthemethodname.Thefollowingcodesnippetshowshowloggingcanbeexecutedwiththelinenumberandthemethodname:

//mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingpath,runtime,fmt,logandtimepackages

import("path""runtime""fmt""log""time")

//checkPointmethodfunccheckPoint()string{pc,file,line,_:=runtime.Caller(1)returnfmt.Sprintf("\033[31m%v%s%s%d\x1b[0m",time.Now(),runtime.FuncForPC(pc).Name(),path.Base(file),line)}

//method1funcmethod1(){fmt.Println(checkPoint())}

//mainmethodfuncmain(){

log.SetFlags(log.LstdFlags|log.Lshortfile)

log.Println("loggingthetimeandflags")

method1()

}

Runthefollowingcommandtoexecutetheprecedingcodesnippet:gorunlog_linenumber.go

Theoutputisasfollows:

GotoolusageTheGotoolcompilercanbeinvokedwiththefollowingcommand:

gobuild-gcflags="-S-N"

Thelistoptionscommandsyntaxisasfollows:gobuild-x

Totesttheraceconditions,youcanusethefollowingcommand:gotest-race

Runningatestmethodbynamecanbedoneusingthefollowingsyntax:gotest-run=method1

ToupdateyourversionofGo,youcanusethefollowingcommand:goget-u

Copyingcanbedonewiththefollowingcommand:goget-d

Togetdepths,youcanusethefollowingcommand:goget-t

Togetalistofsoftware,youcanusethefollowingcommand:golist-f

GoenvironmentvariablesTheGOROOTvariablecanbeconfiguredasanenvironmentvariablewiththiscommand:

exportGOROOT=/opt/go1.7.1

ThePATH variablecanbeconfiguredasanenvironmentvariablewiththiscommand:

exportPATH=$GOROOT/bin:$PATH

TheGOPATHvariablecanbeconfiguredasanenvironmentvariablewiththiscommand:

exportGOPATH=$HOME/go

TheGOPATHvariablecanbeconfiguredinthePATH variablewiththiscommand:

exportPATH=$GOPATH/bin:$PATH

TesttableTestsaredrivenbyatesttable.Thefollowingcodesnippetshowshowatesttablecanbeused:

//mainpackagehasexamplesshown//inGoDataStructuresandalgorithmsbookpackagemain

//importingtestingpackages

import("testing")

funcTestAddition(test*testing.T){

cases:=[]struct{integer1,integer2,resultSumint}{{1,1,2},{1,-1,0},{1,0,1},{0,0,0},{3,2,1},}

for_,cas:=rangecases{varsumintvarexpectedintsum=cas.integer1+cas.integer2expected=cas.resultSumifsum!=expected{test.Errorf("%d+%d=%d,expected%d",cas.integer1,cas.integer2,sum,expected)}}

}

Runthefollowingcommandtoexecutetheprecedingcodesnippet:gotest-runTestAddition-v

Theoutputisasfollows:

ImportingpackagesYoucanimportpackageswiththefollowingstatements.Here,weshowthreedifferentsyntacticaloptions:

import"fmt"

importft"fmt"

import."fmt"

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