Submission #1118273

#	Time	Username	Problem	Language	Result	Execution time	Memory
1118273		vjudge1	Kangaroo (CEOI16_kangaroo)	C++17	100 / 100	13 ms	31736 KiB

kangaroo

#include <bits/stdc++.h>

using namespace std;

#define int long long

const int sz=2e5+5;

const int INF=1e18;

const int MOD=1e9+7;

int dp[2005][2005];

void solve()
{
    int n,cf,cn,cnt=0;
    
    cin>>n>>cf>>cn;
    
    dp[1][1]=1;
    
    for(int i=1;i<=n;i++)
    {
        if(i==cf || i==cn)
            cnt++;
        
        for(int j=1;j<i;j++)
        {
            if(i==cf || i==cn)
            {
                dp[i][j]+=dp[i-1][j]%MOD;
                
                dp[i][j+1]+=dp[i-1][j]%MOD;
            }
            
            else
            {
                dp[i][j+1]+=(dp[i-1][j]*(j+1-cnt))%MOD;
                
                dp[i][j-1]+=(dp[i-1][j]*(j-1))%MOD;
            }
        }
    }
    
    cout<<dp[n][1];
}

signed main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    
    int t=1;
    
    //cin>>t;
    
    
    while(t--)
    {
        solve();
    }
}

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