Submission #1280268

#	Time	Username	Problem	Language	Result	Execution time	Memory
1280268		tvgk	Asceticism (JOI18_asceticism)	C++20	100 / 100	28 ms	1996 KiB

asceticism

#include<bits/stdc++.h>
using namespace std;
#define task "a"
#define ll long long
#define fi first
#define se second
#define ii pair<ll, ll>
const int mxN = 1e5 + 7, MOD = 1e9 + 7;

int n, k;
ll gt[mxN], rev[mxN];

int pw(int j, int mx)
{
    if (!mx)
        return 1;

    ll res = pw(j, mx / 2);
    res = res * res % MOD;
    if (mx % 2)
        return res * j % MOD;
    return res;
}

ll C(int u, int v)
{
    return gt[v] * rev[u] % MOD * rev[v - u] % MOD;
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie();
    cout.tie();
    //freopen(task".INP", "r", stdin);
    //freopen(task".OUT", "w", stdout);

    cin >> n >> k;
    gt[0] = rev[0] = 1;
    for (int i = 1; i <= n + 1; i++)
    {
        gt[i] = gt[i - 1] * i % MOD;
        rev[i] = pw(gt[i], MOD - 2);
    }

    ll ans = 0;
    for (int i = 0; i <= k; i++)
    {
        if (i % 2)
            ans = (ans - C(i, n + 1) * pw(k - i, n) % MOD + MOD) % MOD;
        else
            ans = (ans + C(i, n + 1) * pw(k - i, n)) % MOD;
    }
    cout << ans;
}

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