Submission #901715

#	Time	Username	Problem	Language	Result	Execution time	Memory
901715		aqxa	Tents (JOI18_tents)	C++17	100 / 100	69 ms	432 KiB

tents

// solved 
// if u have < --- > , then the 2 cols and 1 row are not usable by any other 
// iterate over pairs of H (hor), V (vert). 

// count ways to configure only H pairs horizontally (catalan number) 
// next count ways to insert V pairs into the horizontal pairs (already fixed): C(H + V + 1, V) 
// next count ways to configure the heights (should be exact same thing)
// lastly count ways to do the empty squares. if x col and y rows 
// consider u have an array of lenth x and 1 <= a_i <= y
// count the ways to do that (can be precomputed for each x/y) 

#include<iostream>
#include<vector>
using namespace std;
#define ll long long
int mod = 1e9 + 7;
 
int func(int n, int m) {
	vector<ll> dp1(m+1, 0), dp2(m+1, 0), dp3(m+1, 0);
	for (int i = 1; i <= n; i++) {
		for (int j = 1; j <= m; j++) {
			dp3[j] = dp2[j]; //empty
			dp3[j] += (1 + dp2[j-1]) * 4 * j; //one, not connected
			if (j > 1) dp3[j] += (1 + dp2[j - 2]) * (j * (j-1))/2; //2 in the row
			if (i > 0) dp3[j] += (1 + dp1[j-1]) * j  * (i-1);//one col, 2 in the col
			dp3[j] %= mod;
		}
		dp1 = dp2;
		dp2 = dp3;
	}
	return dp2[m];
}
 
int main() {
	int n, m;
	cin >> n >> m;
 
	cout << func(n, m) << endl;
	return 0;
}

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