自己实现的字符串长度求取、复制、连接

int strlen(char* s)
{
    int ret = 0;
    while(*s != 0)
    {
        ret++;
        *s++;
    }
    return ret;
}

char* strcpy(char* dest, char* src)
{
    char* ret = dest;
    while(*dest++ = *src++);
    return ret;
}

char* strcat(char* dest, char* src)
{
    char* ret = dest;//先获取指针地址
    while(*dest != 0)
    {
        dest++;
    }
    while(*dest++ = *src++);
    return ret;
}
//一样返回0，不一样返回1
int strcmp(char* s1, char* s2)
{
    int ret = 0;
    while(*s1 != *s2)
    {
        ret = 1;
        break;
    }
    return ret;
}