UVA 10831 - Gerg's Cake(数论)

UVA 10831 - Gerg's Cake

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

long long a, p;

long long pow_mod(long long x, long long k, long long mod) {
long long ans = 1;
while (k) {
if (k&1) ans = ans * x % mod;
x = x * x % mod;
k >>= 1;
}
return ans;
}

int lederang(long long a, long long p) {
a %= p;
if (a == 0) return 0;
if (pow_mod(a, (p - 1) / 2, p) == 1) return 1;
return -1;
}

int main() {
while (~scanf("%lld%lld", &a, &p) && a != -1) {
if (lederang(a, p) < 0) printf("No\n");
else printf("Yes\n");
}
return 0;
}