Con tr - Pointer

Con tr Pointer n Khai bo n Cc ton t &, *, =, + n Nhc li v truyn tham s a ch n Con tr v mng n Cp pht vng nh ng

Con tr Mt s l do nn s dng n Con tr l kiu d liu lu tr a ch ca cc

vng d liu trong b nh my tnh n Kiu con tr cho php:

Truyn tham s kiu a ch Biu din cc kiu, cu trc d liu ng Lu tr d liu trong vng nh heap

n Con tr c s dng trong hm scanf

Con tr Khai bo trong C Kiu con tr phi c nh ngha trn mt kiu c s c nh ngha trc .

typedef kiucs *Tnkiu; typedef int *PINT; //PINT l kiu con tr - a ch vng nh kiu int

int x; PINT p; //p, p1: bin kiu int * int *p1;

int *pi; long int *p; float *pf; char c, d, *pc; /* c v d kiu char

pc l con tr n char */ double *pd, e, f; /* pd l con tr n double

e and f are double */ char *start, *end;

Con tr Khai bo trong C

0x91A2

0x1132

Con tr - Ton t & n &: ton t ly a ch ca 1 bin n a ch ca tt c cc bin trong chng trnh u

c ch nh t khi khai bo

char g = 'z'; int main() {

char c = 'a'; char *p; p = &c; p = &g; return 0;

}

p c 'a'

0x1132

p g 'z'

0x91A2

n *: ton t truy xut gi tr ca vng nh c qun l bi con tr.

#include char g = 'z'; int main() {

char c = 'a'; char *p; p = &c; printf("%c\n", *p); p = &g; printf("%c\n", *p); return 0;

}

a z

xut gi tr do p ang qun l

Con tr - Ton t *

0x91A2

0x1132 p c

'a' 0x1132

p g 'z'

0x91A2

Con tr - Truyn tham s a ch #include void change(int *v); int main() {

int var = 5; change(&var); printf("main: var = %i\n", var); return 0;

} void change(int *v) {

(*v) *= 100; printf("change: *v = %i\n", (*v));

}

Con tr NULL n Gi tr c bit ch rng con tr khng qun l vng

no. Gi tr ny thng c dng ch mt con tr khng hp l.

#include int main() {

int i = 13; short *p = NULL; if (p == NULL) printf(Con tr khng hp l!\n"); else printf(Gi tr : %0xi\n", *p); return 0;

}

0x15A0

0x15A4

0x15A0

Con tr - Ton t gn = n C s khc bit rt quan trng khi thc hin cc php gn:

int i = 10, j = 14; int *p = &i; int *q = &j; *p = *q;

int i = 10, j = 14; int *p = &i; int *q = &j; p = q;

v:

p i 10

0x15A0 14

q j

0x15A4 14

p i 10

0x15A0 q j 0x15A4

0x15A4 14

0x15A4

Luyn tp in vo trng int main(void) {

int i = 10, j = 14, k; int *p = &i; int *q = &j;

*p += 1; p = &k; *p = *q; p = q; *p = *q;

return 0;

}

i 0x2100

j 0x2104

k 0x1208

p 0x120B

q 0x1210

Con tr v Mng n Bin kiu mng l a ch tnh ca mt vng nh, c xc

nh khi khai bo, khng thay i trong sut chu k sng. n Bin con tr l a ch ng ca mt vng nh, c xc

nh qua php gn a ch khi chng trnh thc thi. #include int main() {

int a[10] = {1, 3, 4, 2, 0}; int *p; p = a; //a = p: sai printf(0x%08X %i 0x%08X %i\n, ); a, a[0], p, *p); return 0;

}

3 4

0x15A0 0x15A2

Con tr - Ton t + vi s nguyn #include int main() {

short a[10] = {1, 3, 5, 2, 0}; short *p = a; printf(0x%08X %i 0x%08X %i\n, ); a, a[0], p, *p); p ++; printf(0x%08X %i 0x%08X %i\n, ); a, a[0], p, *p); (*p) ++; printf(0x%08X %i 0x%08X %i\n, ); a, a[0], p, *p); return 0;

}

1

5 2 0

a

0x15A0

p 0x16B2

Con tr - Luyn tp #include int main() {

int a[10] = {2, 3, 5, 1, 4, 7, 0}; int *p = a; printf(%i %i\n, a[0], *p); p ++; printf(%i %i\n, *p, p[2]); p ++; a[2] = 9; printf(%i %i\n, p[1], *p); p -= 2; printf(%i %i\n, p[3], p[1]); return 0;

}

2 2 3 1 1 9 1 3

Con tr - Cp pht vng nh ng

#include int main() {

int *p = malloc(10*sizeof(int)); p[0] = 1; p[3] = -7; free(p); return 0;

}

n C th ch nh vng mi cho 1 con tr qun l bng cc lnh hm malloc (memory-alloc), calloc (clear-alloc) hoc ton t new ca C++

n Vng nh do lp trnh vin ch nh phi c gii phng bng lnh free (malloc, calloc) hoc ton t delete (new)

Tng kt

n Khai bo n Cc ton t &, *, =, + n Nhc li v truyn tham s a ch n Con tr v mng n Cp pht vng nh ng

Chui k t - String

Chui k t Strings n Mt s qui tc n Nhp / xut n Con tr v chui k t n Mt s hm th vin

Chui k t - Mt s qui tc n Chui k t l mng mt chiu c mi thnh phn l mt

s nguyn c kt thc bi s 0. n K t kt thc (0) cui chui k t thng c gi l

k t null (khng ging con tr NULL). C th ghi l 0 hoc \0 (khng phi ch o).

n c khai bo v truyn tham s nh mng mt chiu.

char s[100]; unsigned char s1[1000];

char first_name[5] = { 'J', 'o', 'h', 'n', '\0' }; char last_name[6] = "Minor"; char other[] = "Tony Blurt"; char characters[7] = "No null";

first_name

last_name

other

characters

Chui k t - V d

'J' 'o' 'h' 'n' 0

'M' 'i' 'n' 'o' 'r' 0

'T' 'o' n

'y' 32 'B' 'l' 'u' 'r' 't' 0

'N' 'o' 32 'n' 'u' 'l' 'l' 0

n C th nhp / xut chui k t s bng cch nhp tng k t ca s

n Hoc s dng cc hm scanf v printf vi k t nh dng %s

n Nhp chui c khong trng dng hm gets

n scanf and gets have a potential overflow problem (use fgets(s, len, stdin) instead to specify the maximum buffer)

char name[100]; printf("Nhap mot chuoi ky tu %s: "); gets(name);

Chui k t - Nhp / xut

char other[] = "Tony Blurt"; printf("%s\n", other);

Lu : kt thc chui #include int main() {

char other[] = "Tony Blurt";

printf("%s\n", other);

other[4] = '\0';

printf("%s\n", other);

return 0; }

Tony Blurt Tony

other

"Blurt" s khng c in ra

'T' 'o' n

'y' 32 'B' 'l' 'u' 'r' 't' 0

Chui k t Mt s hm th vin n Ly di chui

l = strlen(s); n i ton b cc k t ca chui thnh IN HOA

strupr(s); n i ton b cc k t ca chui thnh in thng

strlwr(s);

Chui k t Mt s hm th vin n So snh chui: so snh theo th t t in Phn bit IN HOA in thng: int strcmp(const char *s1, const char *s2);

Khng phn bit IN HOA in thng: int stricmp(const char *s1, const char *s2);

#include #include int main() {

char s1[] = "Minor"; char s2[] = "Tony"; int cmp = strcmp(s1, s2); if (cmp < 0) printf("%s < %s", s1, s2); else if (cmp == 0) printf("%s = %s", s1, s2); else printf("%s > %s", s1, s2); return 0;

}

Chui k t v d strcmp

Minor < Tony

Chui k t Mt s hm th vin n Gn ni dung chui:

o Chp ton b chui source sang chui dest: int strcpy(char *dest, const char *src);

o Chp ti a n k t t source sang dest: int strncpy(char *dest, const char *src, int n);

n To chui mi t chui c:

char *strdup(const char *src);

#include #include int main() {

char s[] = "Tony Blurt"; char s2[100], *s3; strcpy(s2, s); printf("%s\n", s2); strncpy(s2 + 2, "12345,3); printf("%s\n", s2); s3 = strdup(s + 5); printf("%s\n", s3); free(s3); return 0;

}

Chui k t v d strcpy

Tony Blurt To123Blurt Blurt

Chui k t Mt s hm th vin n Ni chui:

char *strcat(char *dest, const char *src);

n Tch chui:

char *strtok(char *s, const char *sep);

Tr v a ch ca on u tin. Mun tch on k tip tham s th nht s l NULL

#include #include #define SEPARATOR "., " int main() {

char s[]= "Thu strtok: 9,123.45"; char *p; p = strtok(s, SEPARATOR); while (p != NULL) { printf("%s\n", p); p = strtok(NULL, SEPARATOR); } return 0;

}

Chui k t v d strtok

Thu strtok: 9 123 45

Chui k t Mt s hm th vin n Tm mt k t trn chui:

char *strchr(const char *s, int c); n Tm mt on k t trn chui:

char *strstr(const char *s1, const char *s2);

#include #include int main() {

char s[]= "Thu tim kiem chuoi"; char *p; p = strchr(s, 'm'); printf("%s\n", p); p = strstr(s, "em"); printf("%s\n", p); return 0;

}

Chui k t v d tm kim

m kiem chuoi em chuoi

#include #include void StrIns(char *s, char *sub) {

int len = strlen(sub); memmove(s + len, s, strlen(s)+1); strncpy(s, sub, len);

} int main() {

char s[]= "Thu chen"; StrIns(s, "123"); printf("%s\n", s); StrIns(s + 8, "45"); printf("%s\n", p); return 0;

}

Chui k t chn mt on k t

123 Thu chen 123 Thu 45chen

#include void StrDel(char *s, int n) {

memmove(s, s + n, strlen(s+n)+1); } int main() {

char s[]= "Thu xoa 12345"; StrDel(s, 4); printf("%s\n", s); StrDel(s + 4, 3); printf("%s\n", p); return 0;

}

Chui k t xa mt on k t

xoa 12345 xoa 45

Tng kt

n Khai bo n Nhp / xut n Con tr v chui k t n Mt s hm th vin n Chn / loi b mt on con