Submission #1113164

#	Time	Username	Problem	Language	Result	Execution time	Memory
1113164		onlk97	Tents (JOI18_tents)	C++14	100 / 100	131 ms	70888 KiB

tents

#include <bits/stdc++.h>
#define int long long
#define x first
#define y second
#define pb push_back
using namespace std;
using pii=pair <int,int>;
using tii=pair <pii,int>;
const int mod=1e9+7LL;
int dp[3010][3010];
void solve(){
    int n,m;
    cin>>n>>m;
    dp[0][0]=1;
    for (int i=0; i<n; i++){
        for (int j=0; j<=m; j++){
            dp[i+1][j]+=dp[i][j];
            dp[i+1][j]%=mod;
            if (j<m){
                dp[i+1][j+1]+=4*dp[i][j]*(m-j);
                dp[i+1][j+1]%=mod;
            }
            if (j<m-1){
                dp[i+1][j+2]+=dp[i][j]*((m-j)*(m-j-1)/2%mod);
                dp[i+1][j+2]%=mod;
            }
            if (i<n-1&&j<m){
                dp[i+2][j+1]+=dp[i][j]*((m-j)*(n-i-1)%mod);
                dp[i+2][j+1]%=mod;
            }
        }
    }
    int ans=0;
    for (int i=0; i<=m; i++) ans=(ans+dp[n][i])%mod;
    cout<<(ans+mod-1)%mod<<'\n';
}
signed main(){
    ios_base::sync_with_stdio(0); cin.tie(0);
    int t=1;
    //cin>>t;
    while (t--) solve();
}

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