Submission #932843

#	Time	Username	Problem	Language	Result	Execution time	Memory
932843		Aiperiii	Kangaroo (CEOI16_kangaroo)	C++14	100 / 100	27 ms	31836 KiB

kangaroo

#include <bits/stdc++.h>
#define int long long
#define ff first
#define ss second
#define all(x) x.begin(),x.end()
#define pb push_back
using namespace std;
const int N=2005,mod=1e9+7;
int dp[N][N];
signed main(){
    ios_base::sync_with_stdio();
    cin.tie(0);cout.tie(0);
    int n,s,t;
    cin>>n>>s>>t;
    dp[0][0]=1;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=n;j++){
            if(i==s or i==t)dp[i][j]=dp[i-1][j]+dp[i-1][j-1]%mod;
            else{
                int x=0;
                if(i>s)x++;
                if(i>t)x++;
                dp[i][j]=dp[i-1][j+1]*j%mod;
                dp[i][j]+=dp[i-1][j-1]*(j-x)%mod;
            }
        }
    }

    cout<<dp[n][1]<<"\n";
}
/*

 */

• Subtask 1: 6 / 6
• Subtask 2: 30 / 30
• Subtask 3: 15 / 15
• Subtask 4: 49 / 49