Submission #1082753

#	TimeUTC-0	Username	Problem	Language	Result	Execution time	Memory
1082753	2024-09-01 13:03:01	toast12	Tents (JOI18_tents)	C++14	100 / 100	234 ms	72588 KiB

tents

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#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int MOD = 1e9+7;
vector<vector<bool>> ready;
vector<vector<ll>> dp;
// there are h rows and w columns left
ll solve(int h, int w) {
    if (h < 0 || w < 0)
        return 0;
    if (h == 0 || w == 0)
        return 1;
    if (ready[h][w])
        return dp[h][w];
    ll ans = 0;
    // place nothing
    ans += solve(h-1, w);
    ans %= MOD;
    // place one tent in this row
    // this eliminates one row, one column, and there are 4 different directions the opening can be
    ans += 4*solve(h-1, w-1)*w;
    ans %= MOD;
    // place two tents in this row
    // this eliminates one row, two columns and you can place the two tents in w choose 2 different ways
    ans += solve(h-1, w-2)*(w*(w-1)/2);
    ans %= MOD;
 
 
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• Subtask 1: 48 / 48
• Subtask 2: 52 / 52