"Wilson theorem" HDU 5391 zball in Tina town

HDU 5391 Zball in Tina Town (Wilson theorem)

Test instructions: Give an n, Beg (n-1). %n equals how much.

Wilson's theorem: When and only if N is a prime number: (n-1)!≡-1 (mod n)
Solution: According to Wilson's theorem, p is the prime number of the answer is n-1. Think of the non-Prime, whose n can be multiplied by the preceding number, then the answer is 0. But the 4 answer exception is 2.

#include <cstdio>
#include <cstring>
#include <iostream>
#include <queue>
#include <stack>
using namespace std;
const int N = 1E5+10;
typedef long long LL;

int main ()
{
    int t;
    scanf ("%d", &t);
    while (t--)
    {
        int i, n;
        int s = 1;
        scanf ("%d", &n);
        for (i = 2; i*i <= n; ++i)
        {
            if (!) ( n% i))
            {
                s = 0;
                break;
            }
        }
        if (n = = 4)
            puts ("2");
        else if (s)
            printf ("%d\n", n-1);
        Else
            puts ("0");
    }
    return 0;
}