【c语言】将两个字符串s1和s2比较不要用strcmp

#include <stdio.h>
int main()
{
int i,ret;
char s1[100],s2[100];
printf("input string1:");
gets(s1);
printf("input string2:");
gets(s2);
i=0;
while((s1[i]==s2[i])&&(s1[i]!='\0'))
i++;
if(s1[i]=='\0'&&s2[i]=='\0')
ret=0;
else
ret=s1[i]-s2[i];
printf("\nresult:%d\n",ret);
return 0;
}