56. (待更新)自实现库函数 mystrlen, mystrcpy, mystrcat, mystrcmp, mystrstr,mystrtok

int myStrlen(const char *src)
{
    int len = 0;
    while(*src++)
    {
        len++;
    }
    return len;
}

char* myStrcpy(char* dest,const char* src)
{
    char *d = dest;
    while(*dest++ == *src++);
    return d;
}

char* myStrcat(char* dest,const char* src)
{
    char *d = dest;
    while(*dest) dest++;
    while(*dest++ = *src++);
    return d;
}

int myStrcmp(const char* s1,const char* s2)
{
#if 0
    for(;(*s1&&*s2)&&(*s1++ == *s2++););
    return *s1-*s2;
#endif
    
#if 0
    for(;(*s1&&*s2)&&(*s1++ == *s2++););
    return *s1-*s2;
    
#endif
    
#if 0
    for(; *s1 && *s2 ;s1++,s2++)
    {
        if(*s1 != *s2)
            break;
    }
    return *s1 - *s2;
#endif
    
#if 0
    for(;;str1++,str2++)
    {
        if(*str1 != *str2)
            return *str1-*str2;
        if(*str1 == 0)//两个字符串同时到结尾
            return 0;
    }
#endif
}

char * myStrstr(char *str, char *subStr)//调用库函数实现
{
    if(*subStr == '')
        return str;
    while(str = strchr(str,*subStr))
    {
        if(strncmp(str,subStr,strlen(subStr)) == 0)
              return str;
        str++;
    }
    return NULL;
}


char * myStrstr(char *str, char *subStr)//纯自实现
{
    if(*subStr == '')//如果subStr是空串,直接返回str
        return str;
    while(*str)
    {
        int i = 0;
        for(;*(str+i) == *(subStr+i);i++)
        {
            if(*(subStr+i+1) == '')
                return str;
        }
        str++;
    }
    return NULL;
}