#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;
}
cout << dp[r][1] << endl;
return 0;
}
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
0 ms |
384 KB |
Output is correct |
| 2 |
Correct |
1 ms |
384 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
0 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 |
0 ms |
384 KB |
Output is correct |
| 6 |
Correct |
1 ms |
512 KB |
Output is correct |
| 7 |
Correct |
0 ms |
384 KB |
Output is correct |
| 8 |
Correct |
0 ms |
384 KB |
Output is correct |
| 9 |
Correct |
0 ms |
384 KB |
Output is correct |
| 10 |
Correct |
0 ms |
384 KB |
Output is correct |
| 11 |
Correct |
1 ms |
360 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
0 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 |
0 ms |
384 KB |
Output is correct |
| 6 |
Correct |
1 ms |
512 KB |
Output is correct |
| 7 |
Correct |
0 ms |
384 KB |
Output is correct |
| 8 |
Correct |
0 ms |
384 KB |
Output is correct |
| 9 |
Correct |
0 ms |
384 KB |
Output is correct |
| 10 |
Correct |
0 ms |
384 KB |
Output is correct |
| 11 |
Correct |
1 ms |
360 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 |
288 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 |
384 KB |
Output is correct |
| 19 |
Correct |
1 ms |
384 KB |
Output is correct |
| 20 |
Correct |
1 ms |
384 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
0 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 |
0 ms |
384 KB |
Output is correct |
| 6 |
Correct |
1 ms |
512 KB |
Output is correct |
| 7 |
Correct |
0 ms |
384 KB |
Output is correct |
| 8 |
Correct |
0 ms |
384 KB |
Output is correct |
| 9 |
Correct |
0 ms |
384 KB |
Output is correct |
| 10 |
Correct |
0 ms |
384 KB |
Output is correct |
| 11 |
Correct |
1 ms |
360 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 |
288 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 |
384 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 |
15 ms |
384 KB |
Output is correct |
| 25 |
Correct |
17 ms |
384 KB |
Output is correct |
| 26 |
Correct |
13 ms |
384 KB |
Output is correct |
| 27 |
Correct |
13 ms |
384 KB |
Output is correct |
| 28 |
Correct |
7 ms |
384 KB |
Output is correct |
