Bai Giang C++ - Smith.N Studio

8/3/2019 Bai Giang C++ - Smith.N Studio

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December 30, 2011 Smith Nguyen Studio.

Smith Nguyen Ebooks. 1

Bi 1 : Cu Trc Ca Mt Chng Trnh C++

C l mt trong nhng cch tt nht bt u hc mt ngn ng lp trnh l bng mtchng trnh. Vy y l chng trnh u tin ca chng ta :

// my first program in C++

#include

int main (){

cout


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(khng bt buc). Ni dung ca hm main tip ngay sau phn khai bo chnh thc cbao trong cc ngoc nhn ( { } ) nh trong v d ca chng ta

cout


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Ch thch theo dng bt u t cp du x (//) cho n cui dng. Ch thch theo khibt u bng/* v kt thc bng */v c th bao gm nhiu dng. Chng ta s thm ccch thch cho chng trnh :

/* my second program in C++

with more comments */

#include

int main (){

cout


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y l dng ch thch. Tt c cc dng bt u bng hai du s (//) c coi l cht thchm chng khng c bt k mt nh hng no n hot ng ca chng trnh. Chng cthc cc lp trnh vin dng gii thch hay bnh phm bn trong m ngun cachng trnh. Trong trng hp ny, dng ch thch l mt gii thch ngn gn nhng gm chng trnh chng ta lm.

#include Cc cu bt u bng du (#) c dng cho preprocessor (ai dch h ti t ny vi).Chng khng phi l nhng dng m thc hin nhng c dng bo hiu cho trnhdch. y cu lnh #include bo cho trnh dch bit cn phi "include"th vin iostream. y l mt th vin vo ra cbn trong C++ v n phi c"include" v n sc dng trong chng trnh. y l cch cin s dng th viniostream

int main ()Dng ny tng ng vi phn bt u khai bo hm main. Hm main l im m tt c

cc chng trnh C++ bt u thc hin. N khng ph thuc vo v tr ca hm ny (u, cui hay gia ca m ngun) m ni dung ca n lun c thc hin u tin khichng trnh bt u. Thm vo , do nguyn nhn ni trn, mi chng trnh C++ uphi tn ti mt hm main.

Theo sau main l mt cp ngoc n bi v n l mt hm. Trong C++, tt c cc hmm sau l mt cp ngoc n () th c ngha l n c th c hoc khng c tham s(khng bt buc). Ni dung ca hm main tip ngay sau phn khai bo chnh thc cbao trong cc ngoc nhn ( { } ) nh trong v d ca chng ta

cout


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cout


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Qua bi trc chng ta bit n s tn ti ca cc bin v cc hng. Trong C++, thao tc vi chng ta s dng cc ton t, l cc t kho v cc du khng c trongbng ch ci nhng li c trn hu ht cc bn phm trn th gii. Hiu bit v chng lrt quan trng v y l mt trong nhng thnh phn cbn ca ngn ng C++.

Ton tgn (=).

Ton t gn dng gn mt gi tr no cho mt bin

a = 5;

gn gi tr nguyn 5 cho bin a. V tri bt buc phi l mt bin cn v phi cth l bt k hng, bin hay kt qu ca mt biu thc.

Cn phi nhn mnh rng ton t gn lun c thc hin t tri sang phiv khng bao gio ngc

a = b;

gn gi tr ca bin a bng gi trang cha trong bin b. Ch rngchng ta ch gngi trca b cho a v s thay i ca b sau s khngnh hng n gi tr ca a.

Mt thuc tnh ca ton t gn trong C++ gp phn gip n vt ln ccngn ng lp trnh khc l vic cho php v phi c th cha cc php gnkhc. V d:

a = 2 + (b = 5);

tng ng vi

b = 5;

a = 2 + b;

V vy biu thc sau cng hp l trong C++

a = b = c = 5;

gn gi tr 5 cho c ba bin a, b v c

Cc ton ts hc ( +, -, *, /, % )

Nm ton t s hc c h trbi ngn ng l:


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+ cng

- tr

* nhn

/ chia

% ly phn d (trong php chia)

Th t thc hin cc ton t ny cng ging nh chng c thc hin trong tonhc. iu duy nht c v hi li vi bn l php ly phn d, k hiu bng duphn trm (%). y chnh l php ton ly phn d trong php chia hai s nguynvi nhau. V d, nu a = 11 % 3;, bin a s mang gi tr 2 v 11 = 3*3 +2.

Cc ton tgn phc hp (+=, -=, *=, /=, %=, >>=,


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c s dng trong biu thc; trong trng hp ngc li (a++) gi tr trong bina c tng sau khi tnh ton. Hy ch s khc bit :

V d 1 V d 2

B=3;A=++B;// A is 4, B is 4

B=3;A=B++;// A is 3, B is 4

Cc ton tquan h ( ==, !=, >, =, Ln hn

< Nh hn

> = Ln hn hoc bng< = Nh hn hoc bng

V d:

(7 == 5)s tr gi trfalse

(6 >= 6)s tr gi trtruett nhin thay v s dng cc s, chng ta c th s dng bt c biu thcno. Cho a=2, b=3 v c=6

(a*b >= c) s tr gi trtrue.

(b+4 < a*c)s tr gi trfalse

Cn ch rng = (mt du bng) lf hon ton khc vi == (hai du bng). Duu tin l mt ton t gn ( gn gi tr ca biu thc bn phi cho bin bn tri)v du cn li (==) l mt ton t quan h nhm so snh xem hai biu thc cbng nhau hay khng.


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Trong nhiu trnh dch c trc chun ANSI-C++ cng nh trong ngn ng C, ccton t quan h khng tr v gi tr logic true hoc false m tr v gi trint vi 0tng ng vi false cn gi tr khc 0 (thng l 1) th tng ng vi true.

Cc ton tlogic ( !, &&, || ).

Ton t! tng ng vi ton t logic NOT, n ch c mt i spha bnphi v vic duy nht m n lm l i ngc gi tr ca i s ttrue sang falsehoc ngc li. V d:

!(5 == 5)tr vfalse v biu thc bn phi (5 == 5) c gi trtrue.

!(6 6)) tr vtrue ( true ||false ).

Ton tiu kin ( ? ).

Ton tiu kin tnh ton mt biu thc v tr v mt gi tr khc tu thuc vobiu thc l ng hay sai. Cu trc ca n nh sau:

condition ? result1 : result2


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C hai cch chuyn i kiu u hp l trong C++. Thm vo ANSI-C++ cnc nhng ton t chuyn i kiu mi c trng cho lp trnh hng i tng.

sizeof()

Ton t ny c mt tham s, c th l mt kiu d liu hay l mt bin v trv kch cbng byte ca kiu hay i tng .

a = sizeof (char);

a s mang gi tr 1 v kiu char lun c kch c1 byte trn mi h thng. Gi trtr v ca sizeofl mt hng s v vy n lun lun c tnh trc khi chngtrnh thc hin.

Cc ton tkhc

Trong C++ cn c mt s cc ton t khc, nh cc ton t lin quan n con trhay lp trnh hng i tng. Chng sc ni n c th trong cc phntng ng.

Thtu tin ca cc ton t

Khi vit cc biu thc phc tp vi nhiu ton hng cc bn c th t hi ton hng no

c tnh trc, ton hng no c tnh sau. V d nh trong biu thc sau:

a = 5 + 7 % 2

c th c hai cch hiu sau:

a = 5 + (7 % 2) vi kt qu l 6, hoca = (5 + 7) % 2 vi kt qu l 0

Cu tr li ng l biu thc u tin. V nguyn nhn ni trn, ngn ng C++ thitlp mt th tu tin gia cc ton t, khng ch ring cc ton t s hc m tt c cc

ton t c th xut hin trong C++. Th tu tin ca chng c lit k trong bng sautheo th t t cao xung thp.

Tht

Ton t M t Associativity


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1 :: scope Tri

2 () [ ] -> . sizeof Tri

3

++ -- tng/gim

Phi

~ o ngc bit

! NOT

& * Ton t con tr

(type) Chuyn i kiu

+ - Dng hoc m

4 * / % Ton t s hc Tri

5 + - Ton t s hc Tri

6 > Dch bit Tri

7 < >= Ton t quan h Tri

8 == != Ton t quan h Tri

9 & ^ |Ton t thao tcbit

Tri

10 && || Ton t logic Tri

11 ?: Ton tiu kin Phi

12= += -= *= /= %=

>>=


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Hu ht cc cu trc iu khin m chng ta s xem xt trong chng ny cho php sdng mt lnh n hay mt khi lnh lm tham s, tu thuc vo chng ta c t ntrong cp ngoc nhn hay khng.

Cu trc iu kin: if v else

Cu trc ny c dng khi mt lnh hay mt khi lnh chc thc hin khi mt iukin no tho mn. Dng ca n nh sau:

if (condition) statement

trong condition l biu thc sc tnh ton. Nu iu kin l true,statementc thc hin. Nu khng statementb b qua (khng thc hin) v chng trnh tiptc thc hin lnh tip sau cu trc iu kin.

V d, on m sau y s vit x is 100 ch khi bin x cha gi tr 100:

if (x == 100)cout


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else if (x < 0)

cout > n;while (n>0) {

cout 0) cn c tho mn.

Chng ta cn phi nhrng vng lp phi kt thc mt im no , vvy bn trong vng lp chng ta phi cung cp mt phng thc no buc condition trthnh sai nu khng th n s lp li mi mi. Trong v


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d trn vng lp phi c lnh --n; lm cho condition trthnh sai saumt s ln lp.

Vng lpdo-while

Dng thc:

do statementwhile (condition);

Chc nng ca n l hon ton ging vng lp while ch tr c mt iu l iukin iu khin vng lp c tnh ton sau khistatementc thc hin, v vystatementsc thc hin t nht mt ln ngay c khi condition khng bao gic tho mn. V d, chng trnh di y s vit ra bt k s no m bn nhpvo cho n khi bn nhp s 0.

// number echoer

#include int main (){

unsigned long n;

do {cout > n;

cout


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Cch thc hot ng ca n nh sau:

1, initializationc thc hin. Ni chung n t mt gi kh ban u chobin iu khin. Lnh ny c thc hin chmt ln.2, conditionc kim tra, nu n l ng vng lp tip tc cn nu

khng vng lp kt thc v statementc b qua.3, statementc thc hin. N c th l mt lnh n hoc l mt khilnh c bao trong mt cp ngoc nhn.4, Cui cng, increasec thc hin tng bin iu khin v vng lpquay trli bc 2.

Sau y l mt v dm ngc s dng vngfor.

// countdown using a for loop

#include

int main ()

{for (int n=10; n>0; n--) {

cout


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Lnhbreak.

S dng breakchng ta c th thot khi vng lp ngay c khi iu kin n ktthc cha c tho mn. Lnh ny c thc dng kt thc mt vng lpkhng xc nh hay buc n phi kt thc gia chng thay v kt thc mt cch

bnh thng. V d, chng ta s dng vic m ngc trc khi n kt thc:

// break loop example

#include

int main (){

int n;

for (n=10; n>0; n--) {cout


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Lnh ny cho php nhy v iu kin ti bt k im no trong chng trnh. Nichung bn nn trnh dng n trong chng trnh C++. Tuy nhin chng ta vn cmt v d dng lnh gotom ngc:

// goto loop example

#include int main (){

int n=10;

loop: ;cout


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default block of instructions

}

N hot ng theo cch sau: switch tnh biu thc v kim tra xem n c bng constant1hay khng, nu ng th n thc hin block of instructions 1 cho n khi tm thy t kho

break, sau nhy n phn cui ca cu trc la chn switch.Cn nu khng, switch s kim tra xem biu thc c bng constant2 hay khng. Nung n s thc hin block of instructions 2 cho n khi tm thy t kho break.Cui cng, nu gi tr biu thc khng bng bt k hng no c chnh trn (bn cth chnh bao nhiu cu lnh case tu thch), chng trnh s thc hin cc lnh trongphn default: nu n tn ti v phn ny khng bt buc phi c.

Hai on m sau l tng ng:

v d switch if-else tng ng

switch (x) {case 1:

cout


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Ch rng lnh switch ch c thc dng so snh mt biu thc vi cc hng. Vvy chng ta khng tht cc bin (case (n*2):) hay cc khong (case (1..3):) v chngkhng phi l cc hng hp l.

style="BORDER-RIGHT: medium none; PADDING-RIGHT: 0cm; BORDER-TOP:

medium none; PADDING-LEFT: 0cm; PADDING-BOTTOM: 0cm; BORDER-LEFT:medium none; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 3pt solid">

Nu bn cn kim tra cc khong hay nhiu gi tr khng phi l hng s hy kt hp cclnh ifv else if

Bi 5 : Hm (I)

Hm l mt khi lnh c thc hin khi n c gi t mt im khc ca chngtrnh. Dng thc ca n nh sau:

type name (argument1,argument2, ...)statement

trong :type l kiu d liu c tr v ca hmname l tn gi ca hm.arguments l cc tham s (c nhiu bao nhiu cng c tu theo nhu cu). Mt tham sbao gm tn kiu d liu sau l tn ca tham s ging nh khi khai bo bin (v d intx) v ng vai tr bn trong hm nh bt k bin no khc. Chng dng truyn thams cho hm khi n c gi. Cc tham s khc nhau c ngn cch bi cc du phy.statement l thn ca hm. N c th l mt lnh n hay mt khi lnh.

Di y l v du tin v hm:

// function example

#include

int addition (int a, int b)

{

int r;r=a+b;

return (r);

}

int main ()

{int z;

z = addition (5,3);

cout


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}

c th hiu c on m ny, trc ht hy nhli nhng iu ni bi u tin:mt chng trnh C++ lun bt u thc hin t hm main. V vy chng ta bt u t

y.

Chng ta c th thy hm main bt u bng vic khai bo bin z kiu int. Ngay sau l mt li gi ti hm addition. Nu chng ta s thy s tng t gia cu trc cali gi hm vi khai bo ca hm:

Cc tham s c vai tr tht r rng. Bn trong hm main chng ta gi hm addition vtruyn hai gi tr: 5 v 3 tng ng vi hai tham sint a v int bc khai bo cho hmaddition.

Vo thi im hm c gi tmain, quyn iu khin c chuyn sang cho hmaddition. Gi tr ca c hai tham s (5 v 3) c copy sang hai bin cc bint a v int bbn trong hm.

Dng lnh sau:

return (r);

kt thc hm addition, v tr li quyn iu khin cho hm no gi n (main) v tiptc chng trnh ci im m n b ngt bi li gi n addition. Nhng thm vo ,gi trc dng vi lnh return (r) chnh l gi trc tr v ca hm.\

Gi tr tr v bi mt hm chnh l gi tr ca hm khi n c tnh ton. V vy bin z sc c gi trc tr v bi addition (5, 3), l 8.

Phm vi hot ng ca cc bin [nhc li]

Bn cn nhrng phm vi hot ng ca cc bin khai bo trong mt hm hay bt k mtkhi lnh no khc ch l hm hay khi lnh v khng th s dng bn ngoi


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chng. V d, trong chng trnh v d trn, bn khng th s dng trc tip cc bin a, bhay r trong hm main v chng l cc bin cc b ca hm addition. Thm vo bncng khng th s dng bin z trc tip bn trong hm addition v n lm bin cc bca hm main.

Tuy nhin bn c th khai bo cc bin ton cc c th s dng chng bt k u,bn trong hay bn ngoi bt k hm no. lm vic ny bn cn khai bo chng bnngoi mi hm hay cc khi lnh, c ngha l ngay trong thn chng trnh.

y l mt v d khc v hm:

// function example#include

int subtraction (int a, int b)

{int r;

r=a-b;

return (r);}

int main (){

int x=5, y=3, z;

z = subtraction (7,2);cout


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z = subtraction (7,2);cout


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Hy tng tng rng chng ta mun to ra mt hm ch hin th mt thng bo lnmn hnh. N khng cn tr v mt gi tr no c, hn na cng khng cn nhn tham sno ht. V vy ngi ta nghra kiu d liu void trong ngn ng C. Hy xem xtchng trnh sau:

// void function example#include

void dummyfunction (void)

{cout


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int x=5, y=3, z;

z = addition ( x , y );

Trong trng hp ny khi chng ta gi hm addition th cc gi tr5 and 3c truyncho hm, khng phi l bn thn cc bin.

n y cc bn c th hi ti: Nh vy th sao, c nh hng g u ? iu ng ni y l khi cc bn thay i gi tr ca cc bin a hay b bn trong hm th cc bin x v yvn khng thay i v chng u c c truyn cho hm ch c gi tr ca chng ctruyn m thi.

Hy xt trng hp bn cn thao tc vi mt bin ngoi bn trong mt hm. V vy bns phi truyn tham s di dng tham s bin nhtrong hm duplicate trong v ddi y:

// passing parameters by reference

#include

void duplicate (int& a, int& b, int& c)

{a*=2;

b*=2;

c*=2;}

int main ()

{int x=1, y=3, z=7;

duplicate (x, y, z);

cout


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Trong v d trn, chng ta lin kt a, b v c vi cc tham s khi gi hm (x, y v z) vmi s thay i vi a bn trong hm snh hng n gi tr ca x v hon ton tng tvi b v y, c v z.

Kiu khai bo tham s theo dng tham s bin s dng du v (&) ch c trong C++.Trong ngn ng C chng ta phi s dng con tr lm vic tng t nh th.

Truyn tham s di dng tham s bin cho php mt hm tr v nhiu hn mt gi tr.V d, y l mt hm tr v s lin trc v lin sau ca tham su tin.

// more than one returning value

#include

void prevnext (int x, int& prev, int& next)

{prev = x-1;

next = x+1;

}

int main ()

{

int x=100, y, z;

prevnext (x, y, z);cout


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{int r;

r=a/b;

return (r);}

int main ()

{cout


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float divide (float a, float b){

return (a/b);

}

int main (){

int x=5,y=2;float n=5.0,m=2.0;

cout


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// factorial calculator#include

long factorial (long a){

if (a > 1)return (a * factorial (a-1));

elsereturn (1);

}

int main ()

{

long l;cout > l;

cout


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y chnh l phn u ca nh ngha hm, ngoi tr:

N khng c bt k lnh no cho hm. iu ny c ngha l n khng bao gmthn hm vi tt c cc lnh thng c bc trong cp ngoc nhn { }.

N kt thc bng du chm phy (;).

Trong phn lit k cc tham s ch cn vit kiu ca chng l . Vic vit tn cacc tham s trong phn khai bo mu l khng bt buc.

V d:

// prototyping

#include

void odd (int a);

void even (int a);

int main (){

int i;do {

cout > i;odd (i);

} while (i!=0);

return 0;}

void odd (int a){if ((a%2)!=0) cout


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u tin chng ta thy khai bo mu ca hai hm odd v even:

void odd (int a);

void even (int a);

cho php hai hm ny c thc s dng trc khi chng c nh ngha hon chnh.Tuy nhin l do c bit gii thch ti sao chng trnh ny li cn t nht mt hm phic khi bo mu l trong odd c mt li gi n even v trong even c mt li gi nodd. V vy nu khng c hm no c khai bo trc th li chc chn s xy ra.

style="BORDER-RIGHT: medium none; PADDING-RIGHT: 0in; BORDER-TOP:

medium none; PADDING-LEFT: 0in; PADDING-BOTTOM: 0in; BORDER-LEFT:

medium none; PADDING-TOP: 0in; BORDER-BOTTOM: windowtext 3pt solid">

Rt nhiu lp trnh vin kinh nghim khuyn rng tt c cc hm nn c khai bo mu. cng l li khuyn ca ti, nht l trong trng hp c nhiu hm hoc chng rt di,

khi vic khai bo tt c cc hm cng mt ch cho php chng ta bit phi gi cchm nh th no, v vy tit kim c thi gian.

Bi 7 : Mng

Mng l mt dy cc phn t c cng kiu c t lin tip trong b nhv c th truyxut n tng phn t bng cch thm mt ch s vo sau tn ca mng.

iu ny c ngha l, v d, chng ta c th lu 5 gi tr kiu int m khng cn phi khaibo 5 bin khc nhau.V d, mt mng cha 5 gi tr nguyn kiu int c tn l billy c thc biu din nh sau:

trong mi mt trng biu din mt phn t ca mng, trong trng hp ny l ccgi tr nguyn kiu int. Chng c nh s t0n 4 v phn tu tin ca mng lunl 0 bt k di ca n l bao nhiu.

Nh bt k bin no khc, mt mng phi c khai bo trc khi c th s dng. Mtkhai bo in hnh cho mt mng trong C++ nh sau:

type name [elements];

trong type l mt kiu d liu hp l (int, float...), name l mt tn bin hp l vtrng elements chnh mng s cha bao nhiu phn t


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V vy, khai bo billy nh trnh by trn chng ta ch cn mt dng n gin nhsau:

int billy [5];

Ch : Trng elements bn trong cp ngoc [] phi l mt gi tr hng khi khai bo mtmng, v mng l mt khi nhtnh c kch cxc nh v trnh bin dch phi c khnng xc nh xem cn bao nhiu b nh cp pht cho mng trc khi cc lnh c thc thc hin.

Khi to mt mng.

Khi khai bo mt mng vi tm hot ng a phng (trong mt hm), theo mc nh ns khng c khi to, v vy ni dung ca n l khng xc nh cho n khi chng ralu cc gi tr ln .

Nu chng ta khai bo mt mng ton cc (bn ngoi tt c cc hm) n sc khi tov tt c cc phn tc t bng 0. V vy nu chng ta khai bo mng ton cc:

int billy [5];

mi phn t ca billy sc khi to l 0:

Nhng thm vo , khi chng ta khai bo mt mng, chng ta c th gn cc gi tr khito cho tng phn t ca n. V d:

int billy [5] = { 16, 2, 77, 40, 12071 };

lnh trn s khai bo mt mng nh sau:


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S phn t trong mng m chng ta khi to vi cp ngoc nhn { } phi bng s phn tca mng c khai bo vi cp ngoc vung [ ]. Bi v iu ny c thc coi lmt s lp li khng cn thit nn C++ cho php trng gia cp ngoc vung, kchthc ca mng c xc nh bng s gi tr gia cp ngoc nhn.

Truy xut n cc phn tca mng.

bt k im no ca chng trnh trong tm hot ng ca mng, chng ta c th truyxut tng phn t ca mng c hay chnh sa nh l i vi mt bin bnh thng.

Cu trc ca n nh sau:

name[index]

Nhtrong v d trc ta c mng billy gm 5 phn t c kiu int, chng ta c th truyxut n tng phn t ca mng nh sau:

V d, lu gi tr 75 vo phn t th ba ca billy ta vit nh sau:

billy[2] = 75;

v, v d, gn gi tr ca phn t th 3 ca billy cho bin a, chng ta vit:

a = billy[2];

V vy, xt v mi phng din, biu thc billy[2] ging nh bt k mt bin kiu int.

Ch rng phn t th ba ca billy l billy[2], v mng bt u t ch s 0. V vy, phnt cui cng s l billy[4]. V vy nu chng ta vit billy[5], chng ta s truy xut nphn t th 6 ca mng v vt qu gii hn ca mng.

Trong C++, vic vt qu gii hn ch s ca mng l hon ton hp l, tuy nhin n cth gy ra nhng vn thc s kh pht hin bi v chng khng to ra nhng li trongqu trnh dch nhng chng c th to ra nhng kt qu khng mong mun trong qutrnh thc hin. Nguyn nhn ca vic ny sc ni n khn khi chng ta bt u sdng con tr.


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Cn phi nhn mnh rng chng ta s dng cp ngoc vung cho hai tc v: u tin lt kch thc cho mng khi khai bo chng v th hai, chnh ch s cho mt phnt c th ca mng khi xem xt n n.

int billy[5]; // khai bo mt mng mi.

billy[2] = 75; // truy xutn mt phn tca mng.

Mt vi thao tc hp l khc vi mng:

billy[0] = a;billy[a] = 75;

b = billy [a+2];

billy[billy[a]] = billy[2] + 5;

// v d vmng#include

int billy [] = {16, 2, 77, 40, 12071};int n, result=0;

int main (){

for ( n=0 ; n


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int jimmy [3][5];

v, v d, cch truy xut n phn t th hai theo chiu dc v th t theo chiu ngangtrong mt biu thc nh sau:

jimmy[1][3]

(hy nhrng ch s ca mng lun bt u t0).

Mng nhiu chiu khng b gii hn bi hai ch s (hai chiu), Chng c th cha bao

nhiu ch s ty thch mc d t kh cn phi dng n mng ln hn 3 chiu. Hy thxem xt lng b nhm mt mng c nhiu ch s cn n. V d:

char century [100][365][24][60][60];

gn mt gi trchar cho mi giy trong mt th k, phi cn n hn 3 t gi trchars!Chng ta s phi cn khong 3GB RAM khai bo n.

Mng nhiu chiu thc ra l mt khi nim tru tng v chng ta c th c kt qutng t vi mng mt chiu bng mt thao tc n gin gia cc ch s ca n:

int jimmy [3][5]; tng ng viint jimmy [15]; (3 * 5 = 15)

Di y l hai v d vi cng mt kt qu nh nhau, mt s dng mng hai chiu vmt s dng mng mt chiu:

// multidimensional array#include

#define WIDTH 5#define HEIGHT 3

int jimmy [HEIGHT][WIDTH];int n,m;

int main ()

{for (n=0;n


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for (m=0;m


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int myarray [40];

ch cn gi hm nh sau:

procedure (myarray);

Di y l mt v d c th

// arrays as parameters

#include

void printarray (int arg[], int length) {for (int n=0; n


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style="BORDER-RIGHT: medium none; PADDING-RIGHT: 0in; BORDER-TOP:

medium none; PADDING-LEFT: 0in; PADDING-BOTTOM: 0in; BORDER-LEFT:medium none; PADDING-TOP: 0in; BORDER-BOTTOM: windowtext 3pt solid">

Mng, c mt chiu v nhiu chiu, khi truyn cho hm nh l mt tham s thng l

nguyn nhn gy li cho nhng lp trnh vin thiu kinh nghim. Cc bn nn c bi3.3. Con tr c th hiu r hn mng hot ng nh th no.

Bi 8 : Xu K T

Trong tt c cc chng trnh chng ta thy cho n gi, chng ta ch s dng cc binkiu s, ch dng biu din cc s. Nhng bn cnh cc bin kiu s cn c cc xu kt, chng cho php chng ta biu din cc chui k t nh l cc t, cu, on vn bn...Cho n gichng ta mi ch dng chng di dng hng ch cha quan tm n ccbin c th cha chng.

Trong C++ khng c kiu d liu cbn lu cc xu k t. c th tha mn nhucu ny, ngi ta s dng mng c kiu char. Hy nhrng kiu d liu ny (char) chc th lu tr mt k tn, bi vy n c dng to ra xu ca cc k tn.

V d, mng sau (hay l xu k t):

char jenny [20];

c th lu mt xu k t vi di cc i l 20 k t. Bn c th tng tng n nhsau:

Kch thc cc i ny khng cn phi lun lun dng n. V d,jenny c th lu xu"Hello" hay "Merry christmas". V cc mng k t c th lu cc xu k t ngn hn di ca n, trong C++ c mt quy c kt thc mt ni dung ca mt xu k tbng mt k t null, c thc vit l '\0'.

Chng ta c th biu dinjenny (mt mng c 20 phn t kiu char) khi lu tr xu k t"Hello" v "Merry Christmas" theo cch sau:


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Ch rng sau ni dung ca xu, mt k t null ('\0') c dng bo hiu kt thcxu. Nhng mu xm biu din nhng gi tr khng xc nh.

Khi to cc xu k t.

V nhng xu k t l nhng mng bnh thng nn chng cng nh cc mng khc. Vd, nu chng ta mun khi to mt xu k t vi nhng gi tr xc nh chng ta c thlm iu tng t nh vi cc mng khc:

char mystring[] = { 'H', 'e', 'l', 'l', 'o', '\0' };

Tuy nhin, chng ta c th khi to gi tr cho mt xu k t bng cch khc: s dng cchng xu k t.

Trong cc biu thc chng ta s dng trong cc v d trong cc chng trc cc hngxu k t xut hin vi ln. Chng c biu din trong cp ngoc kp ("), v d:

"the result is: "

l mt hng xu k t chng ta s dng mt s ch.

Khng ging nh du nhy n (') cho php biu din hng k t, cp ngoc kp (") lhng biu din mt chui k t lin tip, v cui chui mt k t null ('\0') lun c tng thm vo.

V vy chng ta c th khi to xu mystring theo mt trong hai cch sau y:

char mystring [] = { 'H', 'e', 'l', 'l', 'o', '\0' };char mystring [] = "Hello";

Trong c hai trng hp mng (hay xu k t) mystringc khai bo vi kch thc 6k t: 5 k t biu din Hello cng vi mt k t null.

Trc khi tip tc, ti cn phi nhc nhbn rng vic gn nhiu hng nh vic s dngdu ngoc kp (") ch hp l khi khi to mng, tc l lc khai bo mng. Cc biu thctrong chng trnh nh:

mystring = "Hello";

mystring[] = "Hello";

l khng hp l, c cu lnh di y cng vy:

mystring = { 'H', 'e', 'l', 'l', 'o', '\0' };

Vy hy nh: Chng ta ch c th "gn" nhiu hng cho mt mng vo lc khi to n.Nguyn nhn l mt thao tc gn (=) khng th nhn v tri l c mt mng m ch c th


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nhn mt trong nhng phn t ca n. Vo thi im khi to mng l mt trng hpc bit, v n khng thc s l mt lnh gn mc d n s dng du bng (=).

Gn gi tr cho xu k t

V v tri ca mt lnh gn ch c th l mt phn t ca mng ch khng th l c mng,chng ta c th gn mt xu k t cho mt mng kiu char s dng mt phng phpnh sau:

mystring[0] = 'H';mystring[1] = 'e';mystring[2] = 'l';mystring[3] = 'l';mystring[4] = 'o';mystring[5] = '\0';

Nhng r rng y khng phi l mt phng php thc t. gn gi tr cho mt xu kt, chng ta c th s dng lot hm kiu strcpy (string copy), hm ny c nh nghatrong string.h v c thc gi nh sau:

strcpy (string1, string2);

Lnh ny copy ni dung ca string2 sang string1. string2 c th l mt mng, con tr haymt hng xu k t, bi vy lnh sau y l mt cch ng gn xu hng "Hello" chomystring:

strcpy (mystring, "Hello");

V d:

// setting value to string

#include #include

int main (){

char szMyName [20];

strcpy (szMyName,"J. Soulie");

cout


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Mc d chng ta lun c th vit mt hm n gin nh hm setstring di y thchin mt thao tc ging nhstrcpy:

// setting value to string#include

void setstring (char szOut [], char szIn []){

int n=0;

do {szOut[n] = szIn[n];

n++;

} while (szIn[n] != 0);}

int main ()

{char szMyName [20];

setstring (szMyName,"J. Soulie");

cout


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{char mybuffer [100];

cout


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Tt c cc hm ny nhn mt tham s v tr v gi tr s (int, long hoc float). Cc hmny khi kt hp vi phng thc getline ca cin l mt cch ng tin cy hn phngthc cin>> cin khi yu cu ngi s dng nhp vo mt s:

// cin and ato* functions

#include #include

int main ()

{char mybuffer [100];

float price;

int quantity;cout


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Mt s m hnh tt i vi b nhmy tnh chnh l mt ph trong mt thnh ph. Trnmt ph tt c cc ngi nh u c nh s tun t vi mt ci tn duy nht nn nuchng ta ni n s 27 ph Trn Hng o th chng ta c th tm c ni m khnglm ln v ch c mt ngi nh vi s nh vy.

Cng vi cch t chc tng t nh vic nh s cc ngi nh, hiu hnh t chc bnhthnh nhng sn nht, tun t, nn nu chng ta ni n v tr 1776 trong b nhchng ta bit chnh xc nh v ch c mt v tr vi a ch nh vy.

Ton tly a ch (&).

Vo thi im m chng ta khai bo mt bin th n phi c lu tr trong mt v tr cth trong b nh. Ni chung chng ta khng quyt nh ni no bin c t - thtmay mn rng iu c lm tng bi trnh bin dch v hiu hnh, nhngmt khi hiu hnh gn mt a ch cho bin th chng ta c th mun bit bin c lu tru.

iu ny c thc thc hin bng cch t trc tn bin mt du v (&), c ngha l"a chca". V d:

ted = &andy;

s gn cho bin teda ch ca bin andy, v khi t trc tn bin andy du v (&)chng ta khng cn ni n ni dung ca bin m ch ni n a ch ca n trong bnh.

Gi s rng bin andyc t nhc a ch1776 v chng ta vit nh sau:

andy = 25;

fred = andy;ted = &andy;

kt qu s ging nh trong s di y:

Chng ta gn cho fred ni dung ca bin andy nh chng ta lm rt ln nhiu khctrong nhng phn trc nhng vi bin ted chng ta gn a chm hiu hnh lugi tr ca bin andy, chng ta va gi s n l 1776.


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Nhng bin lu tra ch ca mt bin khc (nhtedtrong v d trc) c gi lcon tr. Trong C++ con tr c rt nhiu u im v chng c s dng rt thngxuyn, Tip theo chng ta s thy cc bin kiu ny c khai bo nh th no.

Ton ttham chiu (*)

Bng cch s dng con tr chng ta c th truy xut trc tip n gi trc lu trtrong bin c tr bi n bng cch trc tn bin con tr mt du sao (*) - y cthc dch l "gi trc tr bi". V vy, nu chng ta vit:

beth = *ted;

(chng ta c thc n l: "beth bng gi trc tr bi ted" beth s mang gi tr25, vted bng 1776 v gi tr tr bi 1776 l 25.

Bn phi phn bit c rng ted c gi tr1776, nhng *ted (vi mt du sao ngtrc) tr ti gi trc lu tr trong a ch1776, l 25. Hy ch s khc bit giavic c hay khng c du sao tham chiu.

beth = ted; // beth bng ted ( 1776 )beth = *ted;// beth bnggi trc tr bi( 25 )

Ton tly a ch (&)N c dng nh l mt tin t ca bin v c thc dch l "a ch ca", v vy&variable1 c thc c l "a ch ca variable1".

Ton ttham chiu (*)

N ch ra rng ci cn c tnh ton l ni dung c tr bi biu thc c coi nh lmt a ch. N c thc dch l "gi trc tr bi"..*mypointer c c l "gi trc tr bi mypointer".

Vo lc ny, vi nhng v d vit trn

andy = 25;

ted = &andy;


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bn c th d dng nhn ra tt c cc biu thc sau l ng:

andy == 25

&andy == 1776ted == 1776

*ted == 25

Khai bo bin kiu con tr

V con tr c kh nng tham chiu trc tip n gi tr m chng tr ti nn cn thit phich r kiu d liu no m mt bin con tr tr ti khai bo n. V vy, khai bo ca mtbin con tr s c mu sau:

type * pointer_name;

trong type l kiu d liu c tr ti, khng phi l kiu ca bn thn con tr. V d:

int * number;char * character;

float * greatnumber;

l ba khai bo ca con tr. Mi bin u tr ti mt kiu d liu khc nhau nhng cba u l con tr v chng u chim mt lng b nhnh nhau (kch thc ca mtbin con tr ty thuc vo hiu hnh). nhng d liu m chng tr ti khng chimlng b nhnh nhau, mt kiu int, mt kiu char v ci cn li kiu float.

Ti phi nhn mnh li rng du sao (*) m chng ta t khi khai bo mt con tr ch c

ngha rng: l mt con tr v hon ton khng lin quan n ton t tham chiu mchng ta xem xt trc . n gin ch l hai tc v khc nhau c biu din bicng mt du.

// my first pointer#include

int main (){

int value1 = 5, value2 = 15;

int * mypointer;

mypointer = &value1;

*mypointer = 10;mypointer = &value2;

*mypointer = 20;

cout


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return 0;}

Ch rng gi tr ca value1 v value2c thay i mt cch gin tip. u tin chng

ta gn cho mypointera ch ca value1 dng ton t ly a ch (&) v sau chng tagn 10 cho gi trc tr bi mypointer, l gi trc tr bi value1 v vy chngta sa bin value1 mt cch gin tip

bn c th thy rng mt con tr c th mang mt vi gi tr trong cng mt chngtrnh chng ta s lp li qu trnh vi value2 v vi cng mt con tr.

y l mt v d phc tp hn mt cht:

// more pointers#include

int main (){

int value1 = 5, value2 = 15;

int *p1, *p2;

p1 = &value1; // p1 = a chcavalue1

p2 = &value2; // p2 = a chcavalue2

*p1 = 10; // gi tr tr bi p1 = 10*p2 = *p1; // gi tr tr bi p2 = gi

tr tr bi p1p1 = p2; // p1 = p2 (php gn con

tr)*p1 = 20; // gi tr tr bi p1 = 20

cout


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Con tr v mng.

Trong thc t, tn ca mt mng tng ng vi a ch phn tu tin ca n, gingnh mt con tr tng ng vi a ch ca phn tu tin m n tr ti, v vy thct chng hon ton nh nhau. V d, cho hai khai bo sau:

int numbers [20];int * p;

lnh sau s hp l:

p = numbers;

y p v numbers l tng ng v chng c cng thuc tnh, s khc bit duy nhtl chng ta c th gn mt gi tr khc cho con trp trong khi numbers lun trnphn tu tin trong s 20 phn t kiu int m n c nh ngha vi. V vy, khng

ging nhp - l mt bin con tr bnh thng, numbers l mt con tr hng. Lnhgn sau y l khng hp l:

numbers = p;

bi v numbers l mt mng (con tr hng) v khng c gi tr no c thc gn chocc hng.

V con tr cng c mi tnh cht ca mt bin nn tt c cc biu thc c con tr trong vd di y l hon ton hp l:

// more pointers#include

int main ()

{int numbers[5];

int * p;

p = numbers; *p = 10;p++; *p = 20;

p = &numbers[2]; *p = 30;

p = numbers + 3; *p = 40;

p = numbers; *(p+4) = 50;for (int n=0; n


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Trong bi "mng" chng ta dng du ngoc vung ch ra phn t ca mng mchng ta mun trn. Cp ngoc vung ny c coi nh l ton t offset v nghaca chng khng i khi c dng vi bin con tr. V d, hai biu thc sau y:

a[5] = 0; // a [offset of 5] = 0

*(a+5) = 0; // pointed by (a+5) = 0

l hon ton tng ng v hp l bt ka l mng hay l mt con tr.

Khi to con tr

Khi khai bo con tr c th chng ta s mun chnh r rng chng s tr ti bin no,

int number;

int *tommy = &number;

l tng ng vi:

int number;

int *tommy;tommy = &number;

Trong mt php gn con tr chng ta phi lun lun gn a ch m n tr ti ch khngphi l gi tr m n tr ti. Bn cn phi nhrng khi khai bo mt bin con tr, du sao(*) c dng ch ra n l mt con tr, v hon ton khc vi ton t tham chiu. l hai ton t khc nhau mc d chng c vit vi cng mt du. V vy, cc cu lnhsau l khng hp l:

int number;int *tommy;

*tommy = &number;

Nhi vi mng, trnh bin dch cho php chng ta khi to gi tr m con tr tr tibng gi tr hng vo thi im khai bo bin con tr:

char * terry = "hello";

trong trng hp ny mt khi nhtnh c dnh cha "hello" v mt con tr tr ti

k tu tin ca khi nhny ( l k t h') c gn cho terry. Nu "hello" c luti a ch 1702, lnh khai bo trn c thc hnh dung nh th ny:


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cn phi nhc li rng terry mang gi tr1702 ch khng phi l 'h' hay "hello".

Bin con trterry tr ti mt xu k t v n c thc s dng nh l i vi mtmng (hy nhrng mt mng chn thun l mt con tr hng). V d, nu chng tamun thay k t'o' bng mt du chm than, chng ta c th thc hin vic bng haicch:

terry[4] = '!';

*(terry+4) = '!';

hy nhrng vit terry[4] l hon ton ging vi vit *(terry+4) mc d biu thc thngdng nht l ci u tin. Vi mt trong hai lnh trn xu do terry trn s c gi trnh sau:

Cc php tnh s hc vi pointer

Vic thc hin cc php tnh s hc vi con tr hi khc so vi cc kiu d liu snguyn khc. Trc ht, ch php cng v tr l c php dng. Nhng c cng v tru cho kt qu ph thuc vo kch thc ca kiu d liu m bin con tr tr ti.

Chng ta thy c nhiu kiu d liu khc nhau tn ti v chng c th chim ch nhiuhn hoc t hn cc kiu d liu khc. V d, trong cc kiu s nguyn, charchim 1byte, shortchim 2 byte v long chim 4 byte.

Gi s chng ta c 3 con tr sau:

char *mychar;

short *myshort;

long *mylong;

v chng ln lt tr ti nh1000, 2000 and 3000.


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Nu chng ta vit

mychar++;

myshort++;mylong++;

mychar - nh bn mong i - s mang gi tr 1001. Tuy nhin myshort s mang gi tr2002 v mylong mang gi tr 3004. Nguyn nhn l khi cng thm 1 vo mt con tr thn s tr ti phn t tip theo c cng kiu m n c nh ngha, v vy kch thctnh bng byte ca kiu d liu n tr ti sc cng thm vo bin con tr.

iu ny ng vi c hai php ton cng v tri vi con tr. Chng ta cng hon tonthu c kt qu nh trn nu vit:

mychar = mychar + 1;myshort = myshort + 1;mylong = mylong + 1;

Cn phi cnh bo bn rng c hai ton t tng (++) v gim (--) u c quyn u tinln hn ton t tham chiu (*), v vy biu thc sau y c th dn ti kt qu sai:

*p++;

*p++ = *q++;

Lnh u tin tng ng vi *(p++) iu m n thc hin l tng p (a ch nhm

n tr ti ch khng phi l gi tr tr ti).

Lnh th hai, c hai ton t tng (++) u c thc hin sau khi gi tr ca *q c gncho *p v sau c q v p u tng ln 1. Lnh ny tng ng vi:

*p = *q;

p++;

q++;

Nh ni trong cc bi trc, ti khuyn cc bn nn dng cc cp ngoc n trnhnhng kt qu khng mong mun.

Con tr tr ti con tr

C++ cho php s dng cc con tr tr ti cc con tr khc ging nh l tr ti d liu. lm vic chng ta ch cn thm mt du sao (*) cho mi mc tham chiu.

char a;char * b;


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char ** c;

a = 'z';b = &a;

c = &b;

gi s rng a,b,c c lu cc nh7230, 8092 and 10502, ta c th m ton mtrn nh sau:

im mi trong v d ny l bin c, chng ta c th ni v n theo 3 cch khc nhau, micch s tng ng vi mt gi tr khc nhau:

c l mt bin c kiu (char **) mang gi tr 8092*c l mt bin c kiu (char*) mang gi tr 7230**c l mt bin c kiu (char) mang gi tr 'z'

Con tr khng kiu

Con tr khng kiu l mt loi con trc bit. N c th tr ti bt k loi d liu no,t gi tr nguyn hoc thc cho ti mt xu k t. Hn ch duy nht ca n l d liuc tr ti khng thc tham chiu ti mt cch trc tip (chng ta khng th dngton t tham chiu * vi chng) v di ca n l khng xc nh v v vy chng taphi dng n ton t chuyn kiu d liu hay php gn chuyn con tr khng kiu

thnh mt con tr tr ti mt loi d liu c th.

Mt trong nhng tin ch ca n l cho php truyn tham s cho hm m khng cn chr kiu

// integer increaser#include

void increase (void* data, int type){

switch (type){case sizeof(char) : (*((char*)data))++;

break;

case sizeof(short): (*((short*)data))++;

break;case sizeof(long) : (*((long*)data))++;

break;

6, 10, 13


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}}

int main (){

char a = 5;short b = 9;

long c = 12;increase (&a,sizeof(a));

increase (&b,sizeof(b));

increase (&c,sizeof(c));cout


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int main ()

{

int m,n;m = operation (7, 5, &addition);

n = operation (20, m, minus);cout


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Biu thc u tien c dng cp pht b nhcha mt phn t c kiu type. Lnhth hai c dng cp pht mt khi nh(mt mng) gm cc phn t kiu type.V d:

int * bobby;

bobby = new int [5];

trong trng hp ny, hiu hnh dnh ch cho 5 phn t kiu int trong b nhv trv mt con tr trn u ca khi nh. V vy lc ny bobby trn mt khi nhhpl gm 5 phn tint.

Bn c th hi ti l c g khc nhau gia vic khai bo mt mng vi vic cp pht bnhcho mt con tr nh chng ta va lm. iu quan trng nht l kch thc ca mtmng phi l mt hng, iu ny gii hn kch thc ca mng n kch thc m chngta chn khi thit k chng trnh trong khi cp pht b nhng cho php cp pht bnhtrong qu trnh chy vi kch thc bt k.

B nhng ni chung c qun l bi hiu hnh v trong cc mi trng a nhimc th chy mt lc vi chng trnh c mt kh nng c th xy ra l ht b nh cppht. Nu iu ny xy ra v hiu hnh khng th cp pht b nhnh chng ta yucu vi ton tnew, mt con tr null (zero) sc tr v. V vy cc bn nn kim traxem con tr tr v bi ton tnew c bng null hay khng:

int * bobby;

bobby = new int [5];if (bobby == NULL) {

// error assigning memory. Take measures.

};

Ton tdelete.V b nhng ch cn thit trong mt khong thi gian nht nh, khi n khng cndng n na th n sc gii phng c th cp pht cho cc nhu cu khc trongtng lai. thc hin vic ny ta dng ton tdelete, dng thc ca n nh sau:

deletepointer;

hoc

delete []pointer;


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Biu thc u tin nn c dng gii phng b nhc cp pht cho mt phn tv lnh th hai dng gii phng mt khi nhgm nhiu phn t (mng). Trong huht cc trnh dch c hai biu thc l tng ng mc d chng l r rng l hai ton tkhc nhau.

// rememb-o-matic #include #include

int main (){

char input [100];

int i,n;long * l, total = 0;

cout


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Chng ta s xem xt cch ny v n cng hp l trong C++ v n vn cn c s dngtrong mt s chng trnh.

Hmmallocy l mt hm tng qut cp pht b nhng cho con tr. Cu trc ca n nh sau:

void * malloc (size_t nbytes);

trong nbytes l s byte chng ta mun gn cho con tr. Hm ny tr v mt con trkiu void*, v vy chng ta phi chuyn i kiu sang kiu ca con trch, v d:

char * ronny;ronny = (char *) malloc (10);

on m ny cp pht cho con tr ronny mt khi nh10 byte. Khi chng ta mun cppht mt khi d liu c kiu khc char (ln hn 1 byte) chng ta phi nhn s phn t

mong mun vi kch thc ca chng. Tht may mn l chng ta c ton tsizeof, tont ny tr v kch thc ca mt kiu d liu c th.

int * bobby;

bobby = (int *) malloc (5 * sizeof(int));

on m ny cp pht cho bobby mt khi nhgm 5 s nguyn kiu int, kch ccakiu d liu ny c th bng 2, 4 hay hn ty thuc vo h thng m chng trnh cdch.

Hmcalloc.

calloc hot ng rt ging vi malloc, s khc nhau ch yu l khai bo mu ca n:

void * calloc (size_t nelements, size_t size);

n s dng hai tham s thay v mt. Hai tham s ny c nhn vi nhau c c kchthc tng cng ca khi nhcn cp pht. Thng thng tham su tin (nelements)l s phn t v tham s thc hai (size) l kch thc ca mi phn t. V d, chng ta cthnh ngha bobby vi calloc nh sau:

int * bobby;

bobby = (int *) calloc (5, sizeof(int));

Mt im khc nhau na gia malloc v calloc l calloc khi to tt c cc phn t can v 0.

Hmrealloc.N thay i kch thc ca khi nh c cp pht cho mt con tr.

void * realloc (void *pointer, size_t size);


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tham spointernhn vo mt con tr c cp pht b nhhay mt con tr null, vsize chnh kch thc ca khi nhmi. Hm ny s cp pht size byte b nhcho contr. N c th phi thay i v v tr ca khi nh c th ch cho kch thc mica khi nh, trong trng hp ny ni dung hin thi ca khi nhc copy ti v trmi m bo d liu khng b mt. Con tr mi tr ti khi nhc hm tr v. Nu

khng th thay i kch thc ca khi nhth hm s tr v mt con tr null nhng thamspointerv ni dung ca n s khng b thay i.

Hmfree.Hm ny gii phng mt khi nhng c cp pht bimalloc,calloc hocrealloc.

void free (void *pointer);

Hm ny chc dng gii phng b nhc cp pht bi cc hmmalloc,callocandrealloc.

Bi 11 : Cc Cu Trc

Cc cu trc dliu.

Mt cu trc d liu l mt tp hp ca nhng kiu d liu khc nhau c gp li vimt ci tn duy nht. Dng thc ca n nh sau:

struct model_name {type1 element1;type2 element2;

type3 element3;..

}object_name;

trong model_name l tn ca mu kiu d liu v tham s ty chn object_name mttn hp l cho i tng. Bn trong cp ngoc nhn l tn cc phn t ca cu trc vkiu ca chng.

Nu nh ngha ca cu trc bao gm tham smodel_name (tu chn), tham s ny trthnh mt tn kiu hp l tng ng vi cu trc. V d:

struct products {char name [30];

float price;

} ;

products apple;

products orange, melon;


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Chng ta nh ngha cu trc products vi hai trng: name v price, mi trng cmt kiu khc nhau. Chng ta cng s dng tn ca kiu cu trc (products) khaibo ba i tng c kiu : apple, orange v melon.

Sau khi c khai bo, products trthnh mt tn kiu hp l ging cc kiu cbn nh

int, charhay short.

Trng tu chn object_name c th nm cui ca phn khai bo cu trc dng khaibo trc tip i tng c kiu cu trc. V d, khai bo cc i tng apple, orangev melon nh lm phn trc chng ta cng c th lm theo cch sau:

struct products {

char name [30];float price;

} apple, orange, melon;

Hn na, trong trng hp ny tham smodel_name trthnh tu chn. Mc d numodel_name khng c s dng th chng ta s khng th khai bo thm cc i tngc kiu mu ny.

Mt iu quan trng l cn phn bit r rng u l kiu mu cu trc, u l i tngcu trc. Nu dng cc thut ng chng ta s dng vi cc bin, kiu mu l tn kiud liu cn i tng l cc bin.

Sau khi khai bo ba i tng c kiu l mt mu cu trc xc nh (apple, orangeand melon) chng ta c th thao tc vi cc trng to nn chng. lm vic nychng ta s dng mt du chm (.) chn gia tn i tng v tn trng. V d, chng

ta c th thao tc vi bt k phn t no ca cu trc nh l i vi cc bin chun :

apple.nameapple.price

orange.name

orange.price

melon.namemelon.price

mi trng c kiu d liu tng ng: apple.name, orange.name v melon.name ckiu char[30], v apple.price, orange.price v melon.price c kiu float.

Chng ta tm bit apples, oranges v melons n vi mt v d v cc b phim:

// example about structures

#include

#include #include

Enter title: Alien

Enter year: 1979

My favourite movie is:


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struct movies_t {

char title [50];

int year;} mine, yours;

void printmovie (movies_t movie);

int main ()

{

char buffer [50];

strcpy (mine.title, "2001 A Space

Odyssey");mine.year = 1968;

cout


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Cc cu trc c s dng rt nhiu xy dng csd liu c bit nu chng ta xtn kh nng xy dng cc mng ca chng.

// array of structures#include

#include

#define N_MOVIES 5

struct movies_t {char title [50];

int year;

} films [N_MOVIES];

void printmovie (movies_t movie);

int main (){

char buffer [50];

int n;for (n=0; n


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Nh bt k cc kiu d liu no khc, cc cu trc c thc trn bi con tr. Quytc hon ton ging nhi vi bt k kiu d liu cbn no:


int year;};

movies_t amovie;

movies_t * pmovie;

y amovie l mt i tng c kiu movies_t v pmovie l mt con tr tr ti itng movies_t. OK, by gichng ta sn vi mt v d khc, n s gii thiu mtton t mi:

// pointers to structures

#include #include

struct movies_t {

char title [50];

int year;};

int main ()

{

char buffer[50];

movies_t amovie;

movies_t * pmovie;

pmovie = & amovie;

cout title,50);cout year = atoi (buffer);

cout


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on m trn gii thiu mt iu quan trng: ton t->. y l mt ton t tham chiu

ch dng tr ti cc cu trc v cc lp (class). N cho php chng ta khng phi dngngoc mi khi tham chiu n mt phn t ca cu trc. Trong v d ny chng ta sdng:

movies->title

n c thc dch thnh:

(*movies).title

c hai biu thc movies->title v (*movies).titleu hp l v chng u dng tham

chiu n phn ttitle ca cu trc c tr bi movies. Bn cn phn bit r rng vi:

*movies.title

n tng ng vi

*(movies.title)

lnh ny dng tnh ton gi trc tr bi phn ttitle ca cu trc movies, trongtrng hp ny (title khng phi l mt con tr) n chng c ngha g nhiu. Bn diy tng kt tt c cc kt hp c thc gia con tr v cu trc:

Biu thc M tTng ngvi

movies.title Phn ttitle ca cu trc movies

movies->title

Phn ttitle ca cu trc c tr bi movies (*movies).title

*movies.titleGi trc tr bi phn ttitle ca cu trcmovies

*(movies.title)

Cc cu trc lng nhau

Cc cu trc c thc t lng nhau v vy mt phn t hp l ca mt cu trc c thl mt cu trc khc.


int year;


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}

struct friends_t {

char name [50];

char email [50];

movies_t favourite_movie;} charlie, maria;

friends_t * pfriends = &charlie;

V vy, sau phn khai bo trn chng ta c th s dng cc biu thc sau:

charlie.name

maria.favourite_movie.titlecharlie.favourite_movie.year

pfriends->favourite_movie.year

(trong hai biu thc cui cng l tng ng).

Cc khi nim cbn v cu trc c cp n trong phn ny l hon ton ging vingn ng C, tuy nhin trong C++, cu trc c mrng thm cc chc nng ca mtlp vi tnh cht c trng l tt c cc phn t ca n u l cng cng (public). Bn sc thm cc thng tin chi tit trong phn 4.1, Lp.

Bi 12:Cc Kiu DLiu Do Ngi Dngnh Ngha

Trong bi trc chng ta xem xt mt loi d liu c nh ngha bi ngi dng

(ngi lp trnh): cu trc. Nhng c cn nhiu kiu d liu tnh ngha khc:

Tnh ngha cc kiu dliu (typedef).

C++ cho php chng ta nh ngha cc kiu d liu ca ring mnh da trn cc kiu dliu c. c th lm vic chng ta s s dng t kho typedef, dng thc nhsau:

typedef existing_type new_type_name ;

trong existing_type l mt kiu d liu cbn hay bt k mt kiu d liu nh

ngha v new_type_name l tn ca kiu d liu mi. V d

typedef char C;

typedef unsigned int WORD;

typedef char * string_t;typedef char field [50];


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Trong trng hp ny chng ta nh ngha bn kiu d liu mi: C, WORD, string_tv field kiu char, unsigned int, char* kiu char[50], chng ta hon ton c th s dngchng nh l cc kiu d liu hp l:

C achar, anotherchar, *ptchar1;

WORD myword;string_t ptchar2;field name;

typedef c th hu dng khi bn mun nh ngha mt kiu d liu c dng lp i lpli trong chng trnh hoc kiu d liu bn mun dng c tn qu di v bn mun nc tn ngn hn.

Union

Union cho php mt phn b nhc thc truy xut di dng nhiu kiu d liu

khc nhau mc d tt c chng u nm cng mt v tr trong b nh. Phn khai bo vs dng n tng t vi cu trc nhng chc nng th khc hon ton:

union model_name {type1 element1;type2 element2;type3 element3;

.

.}object_name;

Tt c cc phn t ca unionu chim cng mt ch trong b nh. Kch thc ca n lkch thc ca phn t ln nht. V d:

union mytypes_t {

char c;

int i;

float f;} mytypes;

nh ngha ba phn t

mytypes.cmytypes.i

mytypes.f

mi phn t c mt kiu d liu khc nhau. Nhng v tt c chng u nm cng mt chtrong b nhnn bt k s thay i no i vi mt phn t snh hng ti tt c ccthnh phn cn li.


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Mt trong nhng cng dng ca union l dng kt hp mt kiu d liu cbn vimt mng hay cc cu trc gm cc phn t nh hn. V d:

union mix_t{long l;

struct {short hi;short lo;

} s;

char c[4];

} mix;

nh ngha ba phn t cho php chng ta truy xut n cng mt nhm 4 byte: mix.l,mix.s v mix.c m chng ta c th s dng tu theo vic chng ta mun truy xut nnhm 4 byte ny nh th no. Ti dng nhiu kiu d liu khc nhau, mng v cu trctrong union bn c th thy cc cch khc nhau m chng ta c th truy xut d liu.

Cc unions v danh

Trong C++ chng ta c th s dng cc unions v danh. Nu chng ta t mt union

trong mt cu trc m khng tn (phn i sau cp ngoc nhn { }) union s trthnhv danh v chng ta c th truy xut trc tip n cc phn t ca n m khng cn ntn ca union (c cn cng khng c). V d, hy xem xt s khc bit gia hai phnkhai bo sau y:

union union v danh

struct {

char title[50];

char author[50];union {

float dollars;int yens;

} price;

} book;

struct {

char title[50];

char author[50];union {

float dollars;int yens;

};

} book;


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S khc bit duy nht gia hai on m ny l trong on m u tin chng ta t tncho union (price) cn trong ci th hai th khng. Khi truy nhp vo cc phn tdollarsv yens, trong trng hp th nht chng ta vit:

book.price.dollars

book.price.yens

cn trong trng hp th hai:

book.dollarsbook.yens

Mt ln na ti nhc li rng v n l mt union, hai trng dollars v yensu chimcng mt ch trong b nhnn chng khng th gi hai gi tr khc nhau.

Kiu lit k (enum)

Kiu d liu lit k dng to ra cc kiu d liu cha mt ci g hi c bit mtcht, khng phi kiu s hay kiu k t hoc cc hng true v false. Dng thc ca nnh sau:

enummodel_name{value1,value2,value3,

.

.

} object_name;

V d, chng ta c th to ra mt kiu d liu mi c tn color lu tr cc mu viphn khai bo nh sau:

enum colors_t {black, blue, green, cyan, red, purple, yellow, white};

Ch rng chng ta khng s dng bt k mt kiu d liu cbn no trong phn khaibo. Chng ta to ra mt kiu d liu mi m khng da trn bt k kiu d liu noc sn: kiu color_t, nhng gi tr c th ca kiu color_tc vit trong cp ngocnhn {}. V d, sau khi khai bo kiu lit k, biu thc sau s l hp l:

colors_t mycolor;

mycolor = blue;

if (mycolor == green) mycolor = red;

Trn thc t kiu d liu lit k c dch l mt s nguyn v cc gi tr ca n l cchng s nguyn c chnh. Nu iu ny khng oc chnh, gi tr nguyn tng


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December 30, 2011 Smith Nguyen Studio.ng vi phn tu tin l 0 v cc gi tr tip theo c th tng ln 1, V vy, trongkiu d liu colors_t m chng ta nh ngha trn, white tng ng vi 0, bluetng ng vi 1, green tng ng vi 2 v c tip tc nh th.

Nu chng ta chnh mt gi tr nguyn cho mt gi tr no ca kiu d liu lit k

(trong v d ny l phn tu tin) cc gi tr tip theo s l cc gi tr nguyn tip theo,v d:

enum months_t { january=1, february, march, april,

may, june, july, august,september, october, november, december} y2k;

trong trng hp ny, bin y2k c kiu d liu lit k months_t c th cha mt trong 12gi tr tjanuaryn december v tng ng vi cc gi tr nguyn t1n 12,khng phi 0n 11 v chng ta tjanuary bng 1

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Bai Giang C++ - Smith.N Studio