Submission #47599

#	Time	Username	Problem	Language	Result	Execution time	Memory
47599		qoo2p5	Asceticism (JOI18_asceticism)	C++17	49 / 100	164 ms	93488 KiB

asceticism

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

const int INF = (int) 1e9 + 1e6 + 123;
const ll LINF = (ll) 1e18 + 1e9 + 123;

#define rep(i, s, t) for (auto i = (s); i < (t); ++(i))
#define per(i, s, t) for (auto i = (s); i >= (t); --(i))
#define sz(x) ((int)(x).size())
#define all(x) (x).begin(), (x).end()
#define mp make_pair
#define pb push_back

bool mini(auto &x, const auto &y) {
    if (y < x) {
        x = y;
        return 1;
    }
    return 0;
}

bool maxi(auto &x, const auto &y) {
    if (y > x) {
        x = y;
        return 1;
    }
    return 0;
}

void run();

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    run();
    return 0;
}

const int N = 3003;
const ll MOD = (ll) 1e9 + 7;

ll fact[N], rfact[N];

ll power(ll x, ll y) {
    if (y == 0) {
        return 1;
    }
    if (y % 2 == 0) {
        ll t = power(x, y / 2);
        return t * t % MOD;
    } else {
        return power(x, y - 1) * x % MOD;
    }
}

ll dp[N][N];

void add(ll &x, ll y) {
    x += y;
    x %= MOD;
}

ll cnk(int n, int k) {
    return fact[n] * rfact[n - k] % MOD * rfact[k] % MOD;
}

void run() {
    fact[0] = 1;
    rep(i, 1, N) {
        fact[i] = fact[i - 1] * i % MOD;
    }
    rep(i, 0, N) {
        rfact[i] = power(fact[i], MOD - 2);
    }
    
    dp[0][0] = 1;
    rep(n, 1, N) {
        rep(k, 0, n) {
            add(dp[n][k], dp[n - 1][k] * (k + 1) % MOD);
            if (k > 0) {
                add(dp[n][k], dp[n - 1][k - 1] * (n - k) % MOD);
            }
        }
    }
    
    int n, k;
    cin >> n >> k;
    cout << dp[n][k - 1] << "\n";
}

• Subtask 1: 4 / 4
• Subtask 2: 20 / 20
• Subtask 3: 25 / 25
• Subtask 4: 0 / 51