Submission #158154

#	Time	Username	Problem	Language	Result	Execution time	Memory
158154		fedoseevtimofey	Asceticism (JOI18_asceticism)	C++14	100 / 100	30 ms	1144 KiB

asceticism

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef long double ld;

const int N = 1e5 + 7;

const int md = 1e9 + 7;

void add(int &a, int b) {
    a += b;
    if (a >= md) a -= md;
}

void sub(int &a, int b) {
    a -= b;
    if (a < 0) a += md;
}

int mul(int a, int b) {
    return ((ll)a * b) % md;
}

int power(int a, ll b) {
    int res = 1;
    while (b > 0) {
        if (b & 1) res = mul(res, a);
        a = mul(a, a);
        b >>= 1;
    }
    return res;
}

int inv(int x) {
    return power(x, md - 2);
}

int f[N], rf[N];

int C(int n, int k) {
    return mul(f[n], mul(rf[n - k], rf[k]));
}

int main() {
    ios_base::sync_with_stdio(false); cin.tie(0); cout.setf(ios::fixed); cout.precision(20);
    #ifdef LOCAL
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
    #endif
    int n, k;
    cin >> n >> k;
    --k;
    f[0] = 1;
    for (int i = 1; i < N; ++i) f[i] = mul(f[i - 1], i);
    for (int i = 0; i < N; ++i) rf[i] = inv(f[i]);
    int ans = 0;
    for (int i = 0; i <= k; ++i) {
        int cur = mul(C(n + 1, i), power(k + 1 - i, n));
        if (i % 2 == 0) add(ans, cur);
        else sub(ans, cur);
    }
    cout << ans << '\n';
}

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