Submission #1118250

#	Time	Username	Problem	Language	Result	Execution time	Memory
1118250		vjudge1	Kangaroo (CEOI16_kangaroo)	C++17	6 / 100	1 ms	2384 KiB

kangaroo

#include <bits/stdc++.h>
using namespace std;
#define int long long
const int mod =1000000007;


int dp[3000][3000];

signed main(){
    int n,st,fs;
    int cnt=0;
    cin >> n >> st >> fs;
    dp[1][1] = 1;
    for(int i=2;i<=n;++i){
        if(i == st || i == fs){
            cnt++;
            for(int j=1;j<=n;++j){
                dp[i][j] = ((dp[i-1][j-1] + dp[i-1][j]) % mod);
            }
            continue;
        }
        for(int j=1;j<=n;++j){
            //x _ x _ x 
            dp[i][j] = (dp[i-1][j+1] * j) % mod;
            dp[i][j] = (dp[i][j] + ((dp[i-1][j-1] * (j - cnt)) % mod)) % mod;
        }
    }
    cout << dp[n][1]; 
    //2 4 1 5 3
    //2 5 1 4 3
}

• Subtask 1: 6 / 6
• Subtask 2: 0 / 30
• Subtask 3: 0 / 15
• Subtask 4: 0 / 49