Submission #483628

#	Time	Username	Problem	Language	Result	Execution time	Memory
483628		ymm	Tents (JOI18_tents)	C++17	100 / 100	92 ms	71408 KiB

tents

///
///   You fell for it, fool!
///   Thunder Cross Split Attack!
///

#include <bits/stdc++.h>
#define Loop(x,l,r) for(ll x = ll(l); x < ll(r); ++x)
typedef long long ll;
using namespace std;

const int mod = 1e9+7;
const int N = 3010;
ll dp[N][N];
int n, m;

int main()
{
	ios::sync_with_stdio(false); cin.tie(0);
	cin >> n >> m;
	Loop(i,0,N) dp[0][i] = dp[i][0] = 1;
	Loop(x,1,N) Loop(y,1,N)
	{
		dp[x][y] = dp[x-1][y];
		dp[x][y] += 4*y*dp[x-1][y-1] % mod;
		if(y>1) dp[x][y] += y*(y-1)/2*dp[x-1][y-2] % mod;
		if(x>1) dp[x][y] += y*(x-1)*dp[x-2][y-1] % mod;
		dp[x][y] %= mod;
	}
	cout << (dp[n][m]+mod-1)%mod << '\n';
}

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