Submission #887952

#	Time	Username	Problem	Language	Result	Execution time	Memory
887952		boris_mihov	Tents (JOI18_tents)	C++17	100 / 100	181 ms	78932 KiB

tents

#include <algorithm>
#include <iostream>
#include <numeric>
#include <cassert>
#include <vector>

typedef long long llong;
const int MAXN = 3000 + 10;
const int MOD = 1e9 + 7;

llong dp[MAXN][MAXN];
bool bl[MAXN][MAXN];

llong rec(int n, int m)
{
    if (n < 0 || m < 0)
    {
        return 0;
    }

    if (n == 0 || m == 0)
    {
        return 1;
    }

    if (bl[n][m])
    {
        return dp[n][m];
    }

    bl[n][m] = true;
    dp[n][m] = rec(n - 1, m);
    dp[n][m] += 4 * rec(n - 1, m - 1) * m;
    dp[n][m] += rec(n - 1, m - 2) * m * (m - 1) / 2;
    dp[n][m] += rec(n - 2, m - 1) * m * (n - 1);
    dp[n][m] %= MOD;
    return dp[n][m];
}

int n, m;
int main()
{
    std::cin >> n >> m;
    std::cout << rec(n, m) - 1 << '\n';
    return 0;

}

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