Submission #555502

#	Time	Username	Problem	Language	Result	Execution time	Memory
555502		wenqi	Tents (JOI18_tents)	C++17	100 / 100	291 ms	41700 KiB

tents

// trans rights

#include <bits/extc++.h>
using namespace std;

using ll = long long;
using ull = unsigned long long;

constexpr int mod = 1000000007;

int W, H;
int cache[3069][3069];
bool done[3069][3069];

int dp(int i, int j)
{
    if (i <= 0 or j <= 0)
        return 1;
    bool &d = done[i][j];
    int &ans = cache[i][j];
    if (d)
        return ans;
    ans = (4ll * j * dp(i - 1, j - 1) + dp(i - 1, j)) % mod;
    ll B = ((ll) j * (j - 1)) / 2;
    if (i >= 2)
        ans = (ans + (ll) (i - 1) * j * dp(i - 2, j - 1)) % mod;
    if (j >= 2)
        ans = (ans + B * dp(i - 1, j - 2)) % mod;
    d = true;
    return ans;
}

int main(int argc, const char *argv[])
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin >> W >> H;
    cout << (dp(W, H) - 1 + mod) % mod;
    return 0;
}

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