zoj 2274 Triples

#include <iostream>#include <cstring>using namespace std;#ifdef WIN32#define for if(0);else for#endif#define MAXN 500int a[MAXN];int p[MAXN];int gcd(int a, int b) {return b ? gcd(b, a % b) : a;}int main () {int n;while (1) {cin >> n;if (cin.fail()) break;for (int i = 0; i < n; i ++) cin >> a[i];memset(p, 0, sizeof(p));for (int i = 0; i < n; i ++) {for (int j = 0; j < n; j ++) {if (gcd(a[i], a[j]) == 1) p[i] ++;}}int num = n * (n - 1) * (n - 2) / 6;int temp = 0;for (int i = 0; i < n; i ++) {temp += p[i] * (n - 1 - p[i]);}temp /= 2;num -= temp;cout << num << endl;}return 0;}