strcmp()
C/C++函數，比較兩個字符串
設這兩個字符串為str1，str2，
若str1==str2，則返回零；
若str1<str2，則返回負數；
若str1>str2，則返回正數。

char * my_strcmp(char *key, char *buffer)
{int ret = 0;while ((ret = *key - *buffer)== '\0' && *key != '\0'){key++;buffer++;}if (ret < 0){return -1;}else if (ret > 0){return 1;}return 0;
}
int main()
{char key[] = "apple";char buffer[]="apple";printf("%s\n%s\n%d\n", key,buffer,my_strcmp(key, buffer));system("pause");return 0;
}