Joseph L. Lindo

Algorithms and Data StructuresSir Joseph LindoUniversity of the Cordilleras

Joseph L. Lindo

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Section 1

Algorithm

Why study algorithm?• Make a lot of money out of great algorithm

• $ 10000000000000000?

• Ex. PageRank Algorithm

Why

Joseph L. Lindo

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Section 1

Algorithm

Why study algorithm?• Make significant contribution to the society

• Ex. Viterbi Algorithm

Why

Joseph L. Lindo

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Section 1

Algorithm

Why study algorithm?• Simply to be cool to invent something in computer science or IT field

• Ex. Shortest Path Algorithm

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Joseph L. Lindo

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Algorithm

Definition• An algorithm is a sequence of unambiguous instructions/operations for solving a problem for obtaining a required output for any legitimate input in a finite amount of time

What

Joseph L. Lindo

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Algorithm

What

“computer”+programs

PROBLEM

ALGORITHM

INPUT OUTPUT

Data Structures

Map Navigation AB

Graphs Path

Joseph L. Lindo

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Algorithm

Characteristics• Finiteness

- terminates after a number of steps

• Input- Valid inputs are clearly specified

• Output- can be proven to produce the correct outcome

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Joseph L. Lindo

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Algorithm

Characteristics• Definiteness- rigorously and unambiguously

specified

• Effectiveness- steps are sufficiently simple and basic

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Joseph L. Lindo

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Algorithm

Important Points• Each step of an algorithm is unambiguous

•The range of inputs has to be specified carefully

•The same algorithm can be represented in different ways

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Joseph L. Lindo

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Algorithm

Important Points•The same problem may be solved by different algorithms

•Different algorithms may take different time to solve the same problem – we may prefer one to the other

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Joseph L. Lindo

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Algorithm

Algorithmic ProblemSolving

What1. Understanding the problem

2. Ascertaining the capabilities of a computational device

3. Choose between exact and approximate problem solving

Joseph L. Lindo

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Algorithm

Algorithmic ProblemSolving

What4. Deciding on appropriate data structure

5. Algorithm design techniques

6. Methods of specifying an algorithm(Pseudocode or diagram)

Joseph L. Lindo

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Algorithm

Algorithmic ProblemSolving

What7. Prove an algorithm’s correctness – mathematic induction

8. Analyzing an algorithm – Simplicity, efficiency, optimality

9. Coding an algorithm

Joseph L. Lindo

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Algorithm

Algorithm Analysis• Correctness

• Time efficiency

• Space efficiency

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Joseph L. Lindo

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Algorithm

In generalA good algorithm is a result of repeated effort and rework• Better data structure• Better algorithm design• Better time or space efficiency• Easy to implement• Optimal algorithm

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Joseph L. Lindo

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AlgorithmHow to studyAlgorithm?• Problem

• Representation/data structure in computer

• Operations on representations

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Joseph L. Lindo

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AlgorithmHow to presentAlgorithm?• Human Language

• Graphical representation (Flow Chart) -->

• Pseudo code -->

Sample Problem

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Joseph L. Lindo

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AlgorithmGroup Activity

Write the algorithm in borrowing a book at the University of the Cordilleras.

Represent the algorithm in:• Human Language• Flowchart• Pseudo code

Case

Joseph L. Lindo

Algorithms and Data StructuresSir Joseph LindoUniversity of the Cordilleras

Joseph L. Lindo

PageRank Algorithm

Algorithm

Joseph L. Lindo

PageRank Algorithm

Algorithm

• Created by Larry Page

• The “soul” of Google Search Engine

• Google total assets: $31 billions 2008

Joseph L. Lindo

Viterbi Algorithm

Algorithm

Joseph L. Lindo

Viterbi Algorithm

Algorithm

• conceived by Andrew Viterbi in 1967 as an error-correction scheme for noisy digital communication links

• Viterbi algorithm is a standard component of tens of millions of high-speed modems

Joseph L. Lindo

Viterbi Algorithm

Algorithm

• It is a key building block of modern information infrastructureDigitalcellular, dial-up modems, satellite, deep-space 802.11 wireless LANs. speech recognition, keyword spotting, computational linguistics, and bioinformatics.

Joseph L. Lindo

Shortest Path Algorithm

Algorithm

CLICK HERE FOR MORE INFO

Joseph L. Lindo

Shortest Path Algorithm

Algorithm

• Used in Google Maps

Joseph L. Lindo

Flow Chart Symbols

Algorithm

Joseph L. Lindo

Flow Chart Symbols

Algorithm

Joseph L. Lindo

Flow Chart Symbols

Algorithm

Joseph L. Lindo

Pseudo code

Algorithm

It is a cross between human language and a programming language

Joseph L. Lindo

Name Search Problem

Algorithm

“Create a program that will determine the number of times a name occurs in a list.”

Joseph L. Lindo

Human Language Representation

Algorithm

1. Get the list of names, let's call this nameList2. Get the name to look for, let's call this the keyname3. Compare the keyname to each of the names in nameList4. If the keyname is the same with a name in the list, add 1 to the count5. If all the names have been compared, output the result

Joseph L. Lindo

Flowchart Representation

Algorithm

Joseph L. Lindo

Pseudo code Representation

Algorithm

Let nameList = List of NamesLet keyName = the name to be soughtLet Count = 0For each name in NameList do the followingif name == keyName

Count = Count + 1Display Count