제출 #114236

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
114236		popovicirobert	Asceticism (JOI18_asceticism)	C++14	100 / 100	34 ms	1220 KiB

asceticism

#include <bits/stdc++.h>
#define lsb(x) (x & (-x))
#define ll long long
#define ull unsigned long long
// 217
// 44

using namespace std;

const int MOD = (int) 1e9 + 7;

inline int lgput(int a, int b) {
    int ans = 1;
    while(b > 0) {
        if(b & 1)
            ans = (1LL * ans * a) % MOD;
        b >>= 1;
        a = (1LL * a * a) % MOD;
    }
    return ans;
}

const int MAXN = (int) 1e5 + 5;

int fact[MAXN + 1], invfact[MAXN + 1];

inline int comb(int n, int k) {
    if(n < k) return 0;
    return (1LL * fact[n] * (1LL * invfact[k] * invfact[n - k] % MOD)) % MOD;
}

int main() {
    //ifstream cin("A.in");
    //ofstream cout("A.out");
    int i, n, k;
    ios::sync_with_stdio(false);
    cin.tie(0), cout.tie(0);

    cin >> n >> k;

    fact[0] = invfact[0] = 1;
    for(i = 1; i <= n + 1; i++) {
        fact[i] = (1LL * fact[i - 1] * i) % MOD;
        invfact[i] = lgput(fact[i], MOD - 2);
    }

    k--;

    int ans = 0;
    for(i = 0; i <= k; i++) {
        int cur = (1LL * comb(n + 1, i) * lgput(k - i + 1, n)) % MOD;

        if(i & 1) {
            cur *= -1;
        }

        ans += cur;

        if(ans < 0) {
            ans += MOD;
        }
        if(ans >= MOD) {
            ans -= MOD;
        }
    }

    cout << ans;

    //cin.close();
    //cout.close();
    return 0;
}

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