• 字符的本质是【ASCII码】
• char* s1 = "China"; char* s2 = "China";

  s1 == s2比较的【两个地址】是否相等，而不是【地址指向的内容】是否相等

#include <stdio.h>

int my_strcmp(char* s1, char* s2)
{
    while (*s1 != '\0' && *s2 != '\0')
    {
        if (*s1 > *s2) return 1;
        else if (*s1 < *s2) return -1;
        else
        {
            s1 ++;
            s2 ++;
        }
    }

    if (*s1 == '\0' && *s2 != '\0') return -1;
    else if (*s1 != '\0' && *s2 == '\0') return 1;
    else return 0;
}

// 优化后
int myStrcmp(char* s1, char* s2)
{
    for (; *s1 && *s2; s1 ++, s2 ++)
        if (*s1 != *s2)
            break;
    return *s1 - *s2;
}

int main()
{
    char* s1 = "ahina";
    char* s2 = "zhina";

    int ret = myStrcmp(s1, s2);

    if (ret == 0) printf("s1 == s2\n");
    else if (ret > 0)printf("s1 > s2\n");
    else printf("s1 < s2\n");

    return 0;
}