Submission #1103421

#	Time	Username	Problem	Language	Result	Execution time	Memory
1103421		vjudge1	Kangaroo (CEOI16_kangaroo)	C++14	100 / 100	11 ms	31680 KiB

kangaroo

#include <bits/stdc++.h>
using namespace std;
#define int long long
const int mod = 1e9 + 7;
int n, s, t, f[2010][2010];

signed main() {
	cin >> n >> s >> t;
	f[1][1] = 1;
	for (int i = 2; i <= n; i++) {
		for (int j = 1; j <= i; j++) {
			if (i != s && i != t)
				f[i][j] = (j * (f[i - 1][j + 1]) % mod + (j - (i > s) - (i > t)) * f[i - 1][j - 1] % mod) % mod;
			else
				f[i][j] = (f[i - 1][j - 1] + f[i - 1][j])%mod;
		}
	}
	cout << f[n][1];
	return 0;
}

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