Submission #1224920

#	Time	Username	Problem	Language	Result	Execution time	Memory
1224920		PenguinsAreCute	Tents (JOI18_tents)	C++17	48 / 100	2095 ms	432 KiB

tents

#include <bits/stdc++.h>
using namespace std;
const int MOD = 1e9 + 7;
const int HALF = 5e8 + 4;
int exp(int a, int b) {
	return (b?1LL*exp(1LL*a*a%MOD,b/2)*(b&1?a:1)%MOD:1);
}
int solve(int h, int c) {
	int fact[3005], invfact[3005];
	fact[0] = invfact[0] = 1;
	for(int i=1;i<3005;i++) {
		fact[i] = 1LL * fact[i-1] * i % MOD;
		invfact[i] = exp(fact[i], MOD-2);
	}
	int ans = MOD - 1;
	for(int r1=0;r1<=h;r1++)
		for(int r2=0;r2<=h-r1;r2++)
			for(int c2=0;c2<=c;c2++) {
				int c1 = (r1 + 2 * r2 - 2 * c2);
				if(c1 < 0 || c1 + c2 > c || c1 < 2 * r2)
					continue;
				ans = (ans + 1LL * fact[h] * fact[c] % MOD * invfact[r2] % MOD * invfact[h-r1-r2] % MOD * invfact[c2] % MOD * invfact[c-c1-c2] % MOD * invfact[r1-2*c2] % MOD * exp(2, MOD-1-c2) % MOD * invfact[c1-2*r2] % MOD * exp(2, MOD-1-r2) % MOD * exp(4,r1-2*c2) % MOD * fact[r1-2*c2]) % MOD;
			}
	return ans;
}
int main() {
	int h, c;
	cin >> h >> c;
	cout << solve(h, c);
}

• Subtask 1: 48 / 48
• Subtask 2: 0 / 52