Submission #484630

#	Time	Username	Problem	Language	Result	Execution time	Memory
484630		NekoRolly	Kangaroo (CEOI16_kangaroo)	C++17	100 / 100	11 ms	14132 KiB

kangaroo

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const int N = 2e3+4;
const ll inf = 2e18;
const int mod = 1e9+7;

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

int main(){
	ios_base::sync_with_stdio(0); cin.tie(0);

	cin >> n >> a >> b;

	dp[0][0] = 1;
	for (int i=1; i<=n; i++) for (ll j=1; j<=i; j++){
		if (i == a || i == b) dp[i][j] = (dp[i-1][j-1] + dp[i-1][j])%mod;
		else dp[i][j] = ((j - (i>a) - (i>b)) * dp[i-1][j-1] + j*dp[i-1][j+1])%mod;
	}

	cout << dp[n][1] << "\n";

	return 0;
}

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