Submission #353683

#	Time	Username	Problem	Language	Result	Execution time	Memory
353683		shivensinha4	Tents (JOI18_tents)	C++17	100 / 100	272 ms	70764 KiB

tents

#include "bits/stdc++.h"
using namespace std;
#define for_(i, s, e) for (int i = s; i < (int) e; i++)
#define for__(i, s, e) for (ll i = s; i < e; i++)
typedef long long ll;
typedef vector<int> vi;
typedef pair<int, int> ii;
#define endl '\n'

const ll mod = 1e9+7;

ll ncr(ll n, ll r) {
	if (r == 0) return 1;
	if (r == 1) return n;
	if (r == 2) return ((n*(n-1))/2 % mod);
	assert(false);
}

int main() {
#ifdef mlocal
	freopen("test.in", "r", stdin);
#endif
	
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	
	int n, m; cin >> n >> m;
	ll dp[n+1][m+1]; // [row][empty][light]
	memset(dp, 0, sizeof(dp));
	
	for_(i, 0, m+1) dp[n][i] = 1;
	for (int i = n-1;  i >= 0; i--) {
		for_(emp, 0, m+1) {
			dp[i][emp] = dp[i+1][emp];
			if (emp >= 2) {
				dp[i][emp] += ((dp[i+1][emp-2] * ncr(emp, 2)) % mod);
				if (dp[i][emp] >= mod) dp[i][emp] -= mod;
			}
			
			if (emp >= 1) {
				if (i < n-1) dp[i][emp] += (emp * (n-i-1) * dp[i+2][emp-1]) % mod;
				if (dp[i][emp] >= mod) dp[i][emp] -= mod;
				dp[i][emp] += (((dp[i+1][emp-1] * 4) % mod) * emp) % mod;
				if (dp[i][emp] >= mod) dp[i][emp] -= mod;
			}
		}
	}
	
	cout << (dp[0][m]-1+mod) % mod << endl;
	
	
	return 0;
}

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