zoj 1657 Goldbach's Conjecture

#include "iostream"#include "math.h"using namespace std;int prime(int n){int i, k;k = sqrt(double(n));if(n == 1)return 1;for (i = 2; i <= k; i++){if (n % i == 0)return 0;}return 1;}int main(){int num, count;while (cin >> num && num){count = 0;int p1, p2;for (p1 = 2; p1 <= num/2; p1++){if (prime(p1)){p2 = num - p1;if (prime(p2))count++;}}cout << count << endl;}}