Submission #914337

#	Time	Username	Problem	Language	Result	Execution time	Memory
914337		borisAngelov	Tents (JOI18_tents)	C++17	100 / 100	191 ms	79348 KiB

tents

#include <bits/stdc++.h>

using namespace std;

const int maxn = 3005;
const int mod = 1e9 + 7;

int n, m;

bool bl[maxn][maxn];
long long dp[maxn][maxn];

long long f(int rows, int cols)
{
    if (rows < 0 || cols < 0)
    {
        return 0;
    }

    if (rows == 0 || cols == 0)
    {
        return 1;
    }

    if (bl[rows][cols] == true)
    {
        return dp[rows][cols];
    }

    bl[rows][cols] = true;

    long long ans = 0;

    ans += f(rows - 1, cols);
    ans %= mod;

    ans += (4LL * cols) * f(rows - 1, cols - 1);
    ans %= mod;

    ans += ((1LL * cols) * (1LL * cols - 1LL) / 2LL) * f(rows - 1, cols - 2);
    ans %= mod;

    ans += (1LL * cols) * (1LL * (rows - 1)) * f(rows - 2, cols - 1);
    ans %= mod;

    return dp[rows][cols] = ans;
}

void fastIO()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
}

int main()
{
    fastIO();

    cin >> n >> m;

    cout << f(n, m) - 1 << endl;

    return 0;
}

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