求邮箱验证的算法

#include <stdio.h>
#include <string.h>

int main()
{
    int flag = 0;
    char *ip, str[100] = {0};

    while (scanf("%s", str) != EOF)
    {
        flag = 0;
        flag += str[0] != '@';    //@不能是首位
        ip = strchr(str, '@');    //这个函数不错
        if (!ip)
        {
            puts("NO");continue;
        }
        ip++;

        flag += ip[0] != '.';       //'@'不能和'.'直接相连
        ip = strchr(ip, '.');

        if (ip && 2 == flag)
            puts("YES");
        else    puts("NO");
    }

    return 0;
}