Submission #751709

#	Time	Username	Problem	Language	Result	Execution time	Memory
751709		Dan4Life	Tents (JOI18_tents)	C++17	100 / 100	71 ms	70972 KiB

tents

#include <bits/stdc++.h>
using namespace std;
#define int long long
const int mxN = (int)3e3+10;
const int MOD = (int)1e9+7;
int n, m, dp[mxN][mxN];

int32_t main() {
	cin >> n >> m;
	for(int i = 0; i < mxN; i++) dp[i][0]=dp[0][i]=1;
	for(int i = 1; i <= n; i++){
		for(int j = 1; j <= m; j++){
			dp[i][j] += dp[i-1][j]; // empty row
			dp[i][j] += 4*j*dp[i-1][j-1]; // exactly 1 on row
			if(j>1) dp[i][j] += (j-1)*j/2*dp[i-1][j-2]; // exactly 2 on row
			if(i>1) dp[i][j] += j*(i-1) * dp[i-2][j-1]; //1 on both row and col
			dp[i][j]%=MOD;
		}
	}
	cout << (dp[n][m]+MOD-1)%MOD << "\n";
}

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