1strcmp and strncmp
1 #include <stdio.h> 2 #include <string.h> 3 /* 4 strcmp and strncmp 自实现 5 */ 6 int mystrcmp(const char *str,const char *str1) 7 { 8 for(;*str&&*str1&&*str == *str1;str++,str1++); 9 return *str - *str1; 10 } 11 int mystrncmp(const char *strn,const char *strn1,int n)//2个字符串前n个字符作为子串，然后比较这2个子串的大小 12 { 13 for(;*strn&&*strn1&&*strn == *strn1&& --n;strn++,strn1++); 14 return *strn - *strn1; 15 } 16 int main(void) 17 { 18 //strcmp自实现 19 char *str = "12345688"; 20 char *str1 = "1234567"; 21 int val = mystrcmp(str,str1); 22 if(0 == val) 23 printf("str == str1 "); 24 else if(val > 0) 25 printf("str>str1 "); 26 else 27 printf("str<str1 "); 28 //strncmp自实现 29 char *strn = "131"; 30 char *strn1 = "121"; 31 int val1 = mystrncmp(strn,strn1,3); 32 if(0 == val1) 33 printf("str == str1 "); 34 else if(val1 > 0) 35 printf("str>str1 "); 36 else 37 printf("str<str1 "); 38 39 return 0; 40 }
2.strcpy and strncpy 自实现精炼版本
1 #include <stdio.h> 2 #include <string.h> 3 /* 4 strcpy and strncpy 自实现 5 */ 6 char * mystrcpy(char *str,const char *str1) 7 { 8 char *p = str; 9 while(*str++ = *str1++); 10 11 return p; 12 } 13 char *mystrncpy(char *strn,const char *strn1,int n) 14 { 15 char *pp = strn; 16 while(n--) 17 { 18 *strn++ = *strn1++; 19 } 20 return pp; 21 } 22 int main(void) 23 { 24 //strcpy自实现 25 char str[10]; 26 char *str1 = "123456"; 27 char * p =mystrcpy(str,str1); 28 printf("%s ",str); 29 30 //strncpy自实现 31 char strn[10]; 32 char *strn1 = "123456"; 33 char *pp = mystrncpy(strn,strn1,10); 34 35 printf("%s ",strn); 36 37 return 0; 38 }
3.strcat and strncat 自实现精炼版本
1 #include <stdio.h> 2 #include <string.h> 3 /* 4 strcat and strncat 自实现 5 */ 6 char * mystrcat(char *str,const char *str1) 7 { 8 char *p = str; 9 while(*str)str++; 10 while(*str++ = *str1++); 11 return p; 12 } 13 char *mystrncat(char *strn,const char *strn1,int n) 14 { 15 char *p = strn; 16 while(*strn)strn++; 17 while(n--) 18 *strn++ = *strn1++; 19 return p; 20 } 21 int main(void) 22 { 23 //strcat 自实现 24 char str[20] = "12345"; 25 char *str1 = "678910"; 26 char *p = mystrcat(str,str1); 27 printf("%s ",str); 28 //strncat自实现 29 char strn[20] = "12345"; 30 char *strn1 = "678910"; 31 char *pp = mystrncat(strn,strn1,4); 32 printf("%s ",strn); 33 34 return 0; 35 }