Submission #225470

#	Time	Username	Problem	Language	Result	Execution time	Memory
225470		brcode	Kangaroo (CEOI16_kangaroo)	C++14	100 / 100	38 ms	39680 KiB

kangaroo

#include <iostream>
#include <bits/stdc++.h>

using namespace std;
const int MAXN = 5e3+5;
const long long MOD = 1e9+7;
long long dp[MAXN][MAXN];
int n,a,b;
int main(){
    cin>>n>>a>>b;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=n;j++){
            if(i==1 && j==1){
                dp[i][j] = 1;
                continue;
            }
            if(i==a||i==b){
                dp[i][j] = dp[i-1][j-1]+dp[i-1][j];
                dp[i][j]%=MOD;
            }else{
                dp[i][j] = dp[i-1][j+1]*j;
                dp[i][j]%=MOD;
                dp[i][j]+=dp[i-1][j-1]*(j-(i>a)-(i>b));
                dp[i][j]%=MOD;
            }
        }
    }
    cout<<dp[n][1]<<endl;
}

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