Submission #1032103

#	Time	Username	Problem	Language	Result	Execution time	Memory
1032103		juicy	Tents (JOI18_tents)	C++17	100 / 100	240 ms	35932 KiB

tents

#include <bits/stdc++.h>

using namespace std;

#ifdef LOCAL
#include "debug.h"
#else
#define debug(...) 42
#endif

const int MD = 1e9 + 7;

int F[3001][3001];

int add(int x, int y) {
	if ((x += y) >= MD) {
		x -= MD;
	}
	if (x < 0) {
		x += MD;
	}
	return x;
}

int C2(int N) {
	return N * (N - 1) / 2;
}

int dp(int i, int j) {
	if (i < 0 || j < 0) {
		return 0;
	}
	if (i == 0) {
		return 1;
	}
	if (~F[i][j]) {
		return F[i][j];
	}
	int &res = F[i][j];
	res = 0;
	res = add(res, dp(i - 1, j));
	res = add(res, (long long) dp(i - 1, j - 2) * C2(j) % MD);
	res = add(res, (long long) dp(i - 1, j - 1) * 4 % MD * j % MD);
	res = add(res, (long long) dp(i - 2, j - 1) * (i - 1) % MD * j % MD);
	return res;
}

int main() {
	ios::sync_with_stdio(false); cin.tie(nullptr);

	int N, M; cin >> N >> M;
	memset(F, -1, sizeof(F));
	cout << add(dp(N, M), -1);
	return 0;
}

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