제출 #225470

#	제출 시각UTC-0	아이디	문제	언어	결과	실행 시간	메모리
225470	2020-04-20 15:33:13	brcode	캥거루 (CEOI16_kangaroo)	C++14	100 / 100	38 ms	39680 KiB

kangaroo

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#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;
}
 
 
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