Submission #1091697

#	Time	Username	Problem	Language	Result	Execution time	Memory
1091697		4QT0R	Tents (JOI18_tents)	C++17	100 / 100	146 ms	70740 KiB

tents

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

ll mod=1e9+7;

ll mult(ll a, ll b){
	return (a*b)%mod;
}
ll chose(ll x){
	return ((x*(x-1))/2)%mod;
}

ll dp[3003][3003];

int main(){
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	
	ll n,m;
	cin >> n >> m;
	dp[0][0]=1;
	for (ll i = 1; i<=n; i++)dp[i][0]=1;
	for (ll i = 1; i<=m; i++)dp[0][i]=1;
	for (ll i = 1; i<=n; i++){
		for (ll j = 1; j<=m; j++){
			dp[i][j]=dp[i-1][j];
			dp[i][j]+=mult(4*j,dp[i-1][j-1]);
			if (j>=2)dp[i][j]+=mult(chose(j),dp[i-1][j-2]);
			if (i>=2)dp[i][j]+=mult(mult(i-1,j),dp[i-2][j-1]);
			dp[i][j]=dp[i][j]%mod;
		}
	}
	cout << (dp[n][m]+mod-1)%mod << '\n';
}

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