Submission #1284041

#	Time	Username	Problem	Language	Result	Execution time	Memory
1284041		Trn115	Fences (JOI18_fences)	C++20	0 / 100	0 ms	332 KiB

fences

#include <bits/stdc++.h>

using namespace std;
using ll = long long;

constexpr int N = 3005;
constexpr int MOD = 1e9+7;

int h, w;
ll dp[N][N];

ll mul(ll a, ll b) {
    return a * b % MOD;
}

int main() {
    cin.tie(0)->sync_with_stdio(0);

    cin >> h >> w;
    for (int i = 0; i <= max(h, w); ++i) {
        dp[i][0] = dp[0][i] = 1;
    }
    for (int i = 1; i <= h; ++i) {
        for (int j = 1; j <= w; ++j) {
            if (j >= 2) dp[i][j] += mul(j * (j - 1) / 2, dp[i-1][j-2]);
            dp[i][j] += mul(4 * j, dp[i-1][j-1]);
            if (i >= 2) dp[i][j] += mul(j * (i - 1), dp[i-2][j-1]);
            dp[i][j] += dp[i-1][j];
            dp[i][j] %= MOD;
        }
    }
    cout << (dp[h][w] - 1 + MOD) % MOD;
}

• Subtask 1: 0 / 18
• Subtask 2: 0 / 33
• Subtask 3: 0 / 49