Submission #116647

#	Time	Username	Problem	Language	Result	Execution time	Memory
116647		roseanne_pcy	Tents (JOI18_tents)	C++14	100 / 100	383 ms	35992 KiB

tents

#include <bits/stdc++.h>
using namespace std;
const int md = 1e9+7;
const int maxn = 3e3+5;
int dp[maxn][maxn];
void add(int &a, int b)
{
    a += b;
    if(a>= md) a-= md;
}
int mul(int a, int b)
{
    return (1LL*a*b)%md;
}
int solve(int n, int m)
{
    if(n == 0 || m == 0) return 1;
    if(dp[n][m] != -1) return dp[n][m];
    int &res = dp[n][m];
    res = 0;
    add(res, mul(4*m, solve(n-1, m-1)));
    if(n>= 2) add(res, mul(m*(n-1), solve(n-2, m-1)));
    if(m>= 2) add(res, mul(m*(m-1)/2, solve(n-1, m-2)));
    add(res, solve(n-1, m));
    return res;
}
int main()
{
    int n, m; cin >> n >> m;
    memset(dp, -1, sizeof dp);
    cout << solve(n, m)-1 << endl;
}

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