zoj 3901 Ant(计数)

代码

#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;
typedef long long ll;
const int mod = 1e9+7;

ll pow_mod(ll x, int n) {
ll ret = 1;
while (n) {
if (n&1) ret = ret * x % mod;
x = x * x % mod;
n >>= 1;
}
return ret;
}

ll n, inv2 = pow_mod(2, mod-2), inv6 = pow_mod(6, mod-2);

int main () {
int cas;
scanf("%d", &cas);
while (cas--) {
scanf("%lld", &n);
n %= mod;
ll s = n * (n + 1) % mod * inv2 % mod;
ll p = n * (n + 1) % mod * (2 * n + 1) % mod * inv6 % mod;
ll ans = (n * n % mod * s % mod + p * (n + 1) % mod + s * s % mod + p) % mod;
printf("%lld\n", ans);
}
return 0;
}