Submission #887827

#	Time	Username	Problem	Language	Result	Execution time	Memory
887827		vjudge1	Tents (JOI18_tents)	C++17	100 / 100	132 ms	70996 KiB

tents

#include <bits/stdc++.h>

using namespace std;

#define ll long long int
#define pb push_back
#define mp make_pair
#define pii pair<int, int>
#define all(x) x.begin(), x.end()
#define u_map unordered_map
const int maxn = 3e3 + 5, mod = 1e9 + 7;

ll dp[maxn][maxn];

ll c(int a) {
	return (a * (a - 1) / 2) % mod; 
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    int n, m;
    cin >> n >> m;
    for (int i = 0; i <= n; i++) {
    	dp[i][0] = 1;
    }
    for (int i = 0; i <= m; i++) {
    	dp[0][i] = 1;
    }
    for (int i = 1; i <= n; i++) {
    	for (int j = 1; j <= m; j++) {
    		dp[i][j] = dp[i][j - 1];
    		dp[i][j] = (dp[i][j] + (((i) * 4 % mod) * dp[i - 1][j - 1] % mod)) % mod;
    		dp[i][j] = (dp[i][j] + (((i) * (j - 1) % mod) * dp[i - 1][j - 2] % mod)) % mod;
    		dp[i][j] = (dp[i][j] + c(i) * dp[i - 2][j - 1] % mod) % mod;
       	}
    }
    cout << (dp[n][m] - 1 + mod) % mod;
    return 0;
}
    // dp[1][1] = 4;
    // dp[2][1] = 9;
    // dp[1][2] = 9;
    // dp[1][3] = 15;
    // dp[3][1] = 15;
    // dp[2][3];

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