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Submission #52847

# Submission time Handle Problem Language Result Execution time Memory
52847 2018-06-27T05:09:55 Z Petr(#1971) Kangaroo (CEOI16_kangaroo) C++11
0 / 100
 3 ms 512 KB 
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

ll n, s, f;

ll ans;
const ll mod = int(1e9) + 7;

ll dp[2010][2010];

int main()
{
	cin >> n >> s >> f;
	dp[0][0] = 1;
	for(ll i=1; i<=n; ++i){
		if(i == s || i == f){
			for(int j=0; j<i; ++j)
				(dp[i][j] += dp[i-1][j]) %= mod;
			for(int j=1; j<i; ++j)
				(dp[i][j-1] += dp[i-1][j]) %= mod;
			continue;
		}
		for(ll j=0; j<i; ++j){
			if(j >= 2){
				(dp[i][j-1] += dp[i-1][j] * j % mod * (j-1) % mod) %= mod;
			}
			if(i >= s){
				(dp[i][j-1] += dp[i-1][j] * j % mod) %= mod;
			}
			if(i >= f){
				(dp[i][j-1] += dp[i-1][j] * j % mod) %= mod;
			}
			(dp[i][j+1] += dp[i-1][j]) %= mod;
		}
	}
	cout << dp[n][1] << endl;
	return 0;
}

Subtask #1
0 / 6.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 452 KB Output is correct
2 Incorrect 3 ms 512 KB Output isn't correct

Subtask #2
0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 452 KB Output is correct
2 Incorrect 3 ms 512 KB Output isn't correct

Subtask #3
0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 452 KB Output is correct
2 Incorrect 3 ms 512 KB Output isn't correct

Subtask #4
0 / 49.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 452 KB Output is correct
2 Incorrect 3 ms 512 KB Output isn't correct