Submission #1167508

#	Time	Username	Problem	Language	Result	Execution time	Memory
1167508		OI_Account	Tents (JOI18_tents)	C++20	100 / 100	82 ms	70984 KiB

tents

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;

const int N = 3000;
const ll MOD = 1'000'000'007;

int n, m;
ll dp[N + 10][N + 10];

void calcDP() {
    for (int i = 0; i <= N; i++)
        dp[i][0] = dp[0][i] = 1;
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= m; j++) {
            ll case1 = dp[i - 1][j];
            ll case2 = (j < 2? 0: dp[i - 1][j - 2]) * (((ll) j * (j - 1) / 2ll) % MOD) % MOD;
            ll case3 = (4ll * (ll) j % MOD) * dp[i - 1][j - 1] % MOD;
            ll case4 = (i < 2? 0: ((ll) (i - 1) * j % MOD) * dp[i - 2][j - 1] % MOD);
            dp[i][j] = (case1 + case2 + case3 + case4) % MOD;
        }
}

int main() {
    cin >> n >> m;
    calcDP();
    cout << (dp[n][m] - 1 + MOD) % MOD << flush;
    return 0;
}

• Subtask 1: 48 / 48
• Subtask 2: 52 / 52