Submission #444299

#	Time	Username	Problem	Language	Result	Execution time	Memory
444299		ajpiano	Kangaroo (CEOI16_kangaroo)	C++17	100 / 100	34 ms	31644 KiB

kangaroo

#include <bits/stdc++.h>

using namespace std;

#define f first
#define s second

typedef long long ll;
typedef pair<int, int> pi;

const ll mod = 1e9+7;

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

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