Submission #1118249

#	Time	Username	Problem	Language	Result	Execution time	Memory
1118249		vjudge1	Kangaroo (CEOI16_kangaroo)	C++17	100 / 100	37 ms	31856 KiB

kangaroo

#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define mod 1000000007
int main(){
    int n, cs, cf, fi = 0;
    cin>>n>>cs>>cf;
    vector<vector<ll>> dp(n + 1, vector<ll>(n + 2, 0));
    dp[0][0] = 1;
    for (int i = 1; i <= n; i++){
        if (i == cs || i == cf){
            fi++;
        }
        for (int j = 1; j <= n; j++){
            if (i == cs || i == cf){
                dp[i][j] += dp[i - 1][j - 1];
                dp[i][j] += dp[i - 1][j];
                dp[i][j] %= mod;
                continue;
            }
            dp[i][j] += dp[i - 1][j + 1] * j;
            if (j != 0){
                dp[i][j] += max(j - fi, 0) * dp[i - 1][j - 1];
            }
            dp[i][j] %= mod;
        }
    }
    cout<<dp[n][1];
}

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