#include<stdio.h>#include<assert.h>int my_strcmp(const char*a,const char*b){    while(*a&&*b&&*a==*b)        a++,b++;    if(*a&&*b)        return(*a-*b);    else if(*a&&*b==0)        return 1;    else if(*a==0&&*b)        return-1;    return 0;}int my_strcmp1(const char *str1, const char *str2)  {       assert((str1 != NULL) && (str2 != NULL));       int rt = 0;       while ( !(rt = *(unsigned char *)str1 - *(unsigned char*)str2 ) &&  *str2)       {           str1 ++;            str2 ++;       }       if (rt > 0)        {           rt = 1;       }       else if (rt < 0)       {           rt = -1;       }       return rt;  }  int my_strcmp2(unsigned char *src, unsigned char *dst){        int ret = 0 ;        while( ! (ret = *src - *dst) && *dst)             ++src, ++dst;        if ( ret < 0 )              ret = -1 ;        else if ( ret > 0 )              ret = 1 ;        return( ret );}int my_strcmp3(const char *dest, const char *source)  {     assert((NULL != dest) && (NULL != source));     while (*dest && *source && (*dest == *source))             {                      dest ++;                     source ++;             }     return *dest - *source;}  int my_strcmp4(const char* s1,const char * s2){      for(;*s1==*s2;s1++,s2++)              {            if(*s1 == ‘\0‘)                    return 0;        }      return ((*s1<*s2)?-1:1);}int main(){    char *s1="abc",*s2="abcd";    int m;    m=my_strcmp4(s1,s2);    printf("m=%d\n",m);}

其它：