Submission #328495

#	Time	Username	Problem	Language	Result	Execution time	Memory
328495		EndRay	Kangaroo (CEOI16_kangaroo)	C++17	100 / 100	17 ms	23020 KiB

kangaroo

#include<bits/stdc++.h>
#define ll long long

using namespace std;

const int N = 2000+1, mod = 1e9+7;

int n, a, b;
ll dp[N][N];

int main(){
    ios_base::sync_with_stdio(false);
    cout.tie(0);
    cin.tie(0);
    cin >> n >> a >> b;
    dp[0][0] = 1;
    for(int i = 1; i <= n; ++i){
        if(i == a || i == b)
            for(int j = 1; j <= i; ++j)
                dp[i][j] = (dp[i-1][j-1] + dp[i-1][j])%mod;
        else
            for(int j = 1; j <= i; ++j){
                int not_edges = j - 2 + (i < a) + (i < b);
                dp[i][j] = (dp[i-1][j+1]*j + dp[i-1][j-1]*not_edges)%mod;
            }
    }
    cout << dp[n][1] << "\n";
}

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