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Submission #261537

# Submission time Handle Problem Language Result Execution time Memory
261537 2020-08-11T20:36:59 Z super_j6 Kangaroo (CEOI16_kangaroo) C++14
100 / 100
 19 ms 404 KB 
#include <iostream>
#include <cstdio>
#include <algorithm>
#include <string.h>
using namespace std;
#define endl '\n'
#define ll long long
#define pi pair<int, int>
#define f first
#define s second

const int mod = 1000000007;
const int mxn = 2001;
int n, x, y;
int dp[2][mxn];
int r;

int main(){
	ios::sync_with_stdio(0);
	cin.tie(0);
	
	cin >> n >> x >> y;
	
	dp[r++][0] = 1;
	for(int i = 1, l = 0; i <= n; i++, r ^= 1){
		int t = i == x || i == y;
		dp[r][0] = 0;
		for(int j = 1; j <= n; j++){
			if(t){
				dp[r][j] = (dp[!r][j] + dp[!r][j - 1]) % mod;
			}else{
				dp[r][j] = ((ll)max(0, j - l) * dp[!r][j - 1] + (ll)j * dp[!r][j + 1]) % mod;
			}
		}
		l += t;
	}
	r ^= 1;
	
	cout << dp[r][1] << endl;

	return 0;
}

Subtask #1
6.0 / 6.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 384 KB Output is correct
2 Correct 1 ms 384 KB Output is correct

Subtask #2
30.0 / 30.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 384 KB Output is correct
2 Correct 1 ms 384 KB Output is correct
3 Correct 1 ms 384 KB Output is correct
4 Correct 1 ms 384 KB Output is correct
5 Correct 1 ms 384 KB Output is correct
6 Correct 0 ms 384 KB Output is correct
7 Correct 1 ms 384 KB Output is correct
8 Correct 1 ms 384 KB Output is correct
9 Correct 0 ms 384 KB Output is correct
10 Correct 1 ms 384 KB Output is correct
11 Correct 1 ms 384 KB Output is correct

Subtask #3
15.0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 384 KB Output is correct
2 Correct 1 ms 384 KB Output is correct
3 Correct 1 ms 384 KB Output is correct
4 Correct 1 ms 384 KB Output is correct
5 Correct 1 ms 384 KB Output is correct
6 Correct 0 ms 384 KB Output is correct
7 Correct 1 ms 384 KB Output is correct
8 Correct 1 ms 384 KB Output is correct
9 Correct 0 ms 384 KB Output is correct
10 Correct 1 ms 384 KB Output is correct
11 Correct 1 ms 384 KB Output is correct
12 Correct 1 ms 384 KB Output is correct
13 Correct 1 ms 384 KB Output is correct
14 Correct 1 ms 384 KB Output is correct
15 Correct 1 ms 384 KB Output is correct
16 Correct 1 ms 384 KB Output is correct
17 Correct 1 ms 384 KB Output is correct
18 Correct 1 ms 404 KB Output is correct
19 Correct 1 ms 384 KB Output is correct
20 Correct 1 ms 384 KB Output is correct

Subtask #4
49.0 / 49.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 384 KB Output is correct
2 Correct 1 ms 384 KB Output is correct
3 Correct 1 ms 384 KB Output is correct
4 Correct 1 ms 384 KB Output is correct
5 Correct 1 ms 384 KB Output is correct
6 Correct 0 ms 384 KB Output is correct
7 Correct 1 ms 384 KB Output is correct
8 Correct 1 ms 384 KB Output is correct
9 Correct 0 ms 384 KB Output is correct
10 Correct 1 ms 384 KB Output is correct
11 Correct 1 ms 384 KB Output is correct
12 Correct 1 ms 384 KB Output is correct
13 Correct 1 ms 384 KB Output is correct
14 Correct 1 ms 384 KB Output is correct
15 Correct 1 ms 384 KB Output is correct
16 Correct 1 ms 384 KB Output is correct
17 Correct 1 ms 384 KB Output is correct
18 Correct 1 ms 404 KB Output is correct
19 Correct 1 ms 384 KB Output is correct
20 Correct 1 ms 384 KB Output is correct
21 Correct 2 ms 384 KB Output is correct
22 Correct 2 ms 384 KB Output is correct
23 Correct 2 ms 384 KB Output is correct
24 Correct 16 ms 384 KB Output is correct
25 Correct 13 ms 384 KB Output is correct
26 Correct 19 ms 384 KB Output is correct
27 Correct 17 ms 384 KB Output is correct
28 Correct 7 ms 384 KB Output is correct