Submission #961268

#	Time	Username	Problem	Language	Result	Execution time	Memory
961268		n3rm1n	Tents (JOI18_tents)	C++17	100 / 100	307 ms	71032 KiB

tents

#include<bits/stdc++.h>
#define endl '\n'
using namespace std;
const int MAXN = 3e3 + 10;
void speed()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
}
int n, m;
long long dp[MAXN][MAXN];
long long mod = 1e9 + 7;
void solve()
{
    cin >> n >> m;
    for (int i = 0; i <= n; ++ i)
        dp[i][0] = 1;
    for (int j = 0; j <= m; ++ j)
        dp[0][j] = 1;
    for (long long i = 1; i <= n; ++ i)
    {
        for (long long j = 1; j <= m; ++ j)
        {
            /// 0.
            dp[i][j] = dp[i-1][j];
            /// 1. x .... x
            if(j >= 2)
            {
                dp[i][j] += (dp[i-1][j-2] * ((j * (j - 1) / 2) % mod)) % mod;
                dp[i][j] %= mod;
            }
            /// 2. x
            ///    .
            ///    .
            ///    x
            if(i >= 2)
            {
                dp[i][j] += dp[i-2][j-1] * (i-1) * j;
                dp[i][j] %= mod;
            }
            /// 3. x
            dp[i][j] += (dp[i-1][j-1] * j * 4) % mod;
            dp[i][j] %= mod;
        }
    }
    long long ans = (dp[n][m] + mod - 1) % mod;
    cout << ans << endl;
}
int main()
{
    speed();
    solve();
    return 0;
}

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