Submission #723152

#	Time	Username	Problem	Language	Result	Execution time	Memory
723152		Sohsoh84	Asceticism (JOI18_asceticism)	C++17	100 / 100	24 ms	2004 KiB

asceticism

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef pair<ll, ll> pll;

#define all(x)			(x).begin(),(x).end()
#define X			first
#define Y			second
#define sep			' '
#define endl			'\n'
#define debug(x)		cerr << #x << ": " <<  x << endl;

const ll MAXN = 1e5 + 10;
const ll MOD = 1e9 + 7;

inline ll poww(ll a, ll b) {
	ll ans = 1;
	while (b) {
		if (b & 1) ans = ans * a % MOD;
		a = a * a % MOD;
		b >>= 1;
	}

	return ans;
}

ll fact[MAXN], inv[MAXN];

inline ll C(ll k, ll n) {
	if (k < 0 || k > n) return 0;
	return fact[n] * inv[k] % MOD * inv[n - k] % MOD;
}

int main() {
	ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
	fact[0] = inv[0] = 1;
	for (int i = 1; i < MAXN; i++) {
		fact[i] = fact[i - 1] * i % MOD;
		inv[i] = poww(fact[i], MOD - 2);
	}

	ll ans = 0;
	ll n, k;
	cin >> n >> k;
	for (int i = 0; i <= k; i++) {
		ans = (ans + MOD + (i & 1 ? -1 : 1) * C(i, n + 1) * poww(k - i, n) % MOD) % MOD;
	}

	cout << ans << endl;
	return 0;
}

• Subtask 1: 4 / 4
• Subtask 2: 20 / 20
• Subtask 3: 25 / 25
• Subtask 4: 51 / 51