Submission #370951

#	Time	Username	Problem	Language	Result	Execution time	Memory
370951		blue	Asceticism (JOI18_asceticism)	C++17	100 / 100	138 ms	1388 KiB

asceticism

#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;

long long mod = 1'000'000'007;
long long fact[100002];

long long pow(long long b, long long e)
{
    if(e == 0) return 1;
    if(e % 2) return (b * pow(b, e-1)) % mod;
    else
    {
        long long temp = pow(b, e/2);
        return (temp*temp) % mod;
    }
}

long long choose(long long n, long long k)
{
    return (((fact[n] * pow(fact[k], mod-2)) % mod) * pow(fact[n-k], mod-2)) % mod;
}

int main()
{
    fact[0] = 1;
    for(long long i = 1; i <= 100001; i++) fact[i] = (fact[i-1] * i) % mod;

    long long N, K;
    cin >> N >> K;

    long long ans = 0;

    for(long long i = 0; i <= K; i++)
    {
        // long long temp = (mod +  (pow(-1, i) * ((choose(N-1, K) * pow(K-i, N)) % mod) )    ) % mod;
        long long temp = choose(N+1, i) * pow(K-i, N);
        temp = temp % mod;

        // cout << choose(N+1, K) << ' ' << pow(K-i, N) << '\n';
        // cout << temp << '\n';

        if(i % 2 == 0) ans = (ans + temp) % mod;
        else ans = (mod + ans - temp) % mod;
    }

    cout << ans << '\n';
}

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