Submission #465451

#	Time	Username	Problem	Language	Result	Execution time	Memory
465451		fuad27	Kangaroo (CEOI16_kangaroo)	C++17	100 / 100	31 ms	31908 KiB

kangaroo

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
#define mod 1000000007
#define MAXN 2010
#define int long long
void solve() {
	ll n, s , e;
	cin >> n >> s >> e;
	ll dp[n+10][n+10] = {0};
	dp[1][1] = 1;
	for(int i = 2;i<=n;i++) {
		for(int j = 1;j<=i;j++) {
			if(i == s or i == e) {
				dp[i][j] = (dp[i-1][j-1]+dp[i-1][j])%mod;
			}
			else {
				dp[i][j] = (dp[i-1][j+1]*j%mod + dp[i-1][j-1] * (j - (s<i) - (e<i))%mod)%mod;
			}
		}
	}
	cout<<dp[n][1]<<endl;
}
int32_t main () {/*
	#ifndef ONLINE_JUDGE
	freopen("stdin", "r", stdin);
	freopen("stdout", "w", stdout);
	freopen("stderr", "w", stderr);
	#endif*/
	//cin >> t;
		solve();
	return 0;
}

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