Submission #799876

#	Time	Username	Problem	Language	Result	Execution time	Memory
799876		phoenix	Tents (JOI18_tents)	C++17	100 / 100	94 ms	71068 KiB

tents

#include<bits/stdc++.h>

using namespace std;
using ll = long long;

const int N = 3000;
const int MOD = 1e9 + 7;
ll dp[N + 10][N + 10];

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);cout.tie(0);
    int n, m;
    cin >> n >> m;
    for(int i = 0; i <= n; i++) dp[i][0] = 1;
    for(int j = 0; j <= m; j++) dp[0][j] = 1;
    for(int i = 1; i <= n; i++) {
        for(int j = 1; j <= m; j++) {
            dp[i][j] += dp[i - 1][j];
            dp[i][j] += 4 * j * dp[i - 1][j - 1] % MOD;
            if(j > 1) dp[i][j] += j * (j - 1) / 2 * dp[i - 1][j - 2] % MOD;
            if(i > 1) dp[i][j] += (i - 1) * j * dp[i - 2][j - 1] % MOD;
            dp[i][j] %= MOD;
        }
    }
    cout << (dp[n][m] - 1 + MOD) % MOD;
}

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