#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int MOD = 1e9+7;
const int MAXN = 2001;
int dp[MAXN][MAXN];
int n, a, b;
int main() {
ios_base::sync_with_stdio(false); cin.tie(NULL);
cin >> n >> a >> b;
a--; b--;
dp[0][0] = 1;
for (int i = 0; i < n; i++) {
for (int j = 1; j <= min(i+1, n-i); j++) {
if (i == a || i == b) {
dp[i+1][j] = dp[i][j]+dp[i][j-1];
dp[i+1][j] %= MOD;
}
else {
dp[i+1][j] = ((ll) (j-(i >= a)-(i >= b))*dp[i][j-1]+(ll)j*dp[i][j+1]) % MOD;
}
}
}
cout << dp[n][1] << "\n";
}
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
1 ms |
212 KB |
Output is correct |
| 2 |
Correct |
1 ms |
340 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
1 ms |
212 KB |
Output is correct |
| 2 |
Correct |
1 ms |
340 KB |
Output is correct |
| 3 |
Correct |
1 ms |
340 KB |
Output is correct |
| 4 |
Correct |
1 ms |
592 KB |
Output is correct |
| 5 |
Correct |
1 ms |
468 KB |
Output is correct |
| 6 |
Correct |
1 ms |
468 KB |
Output is correct |
| 7 |
Correct |
1 ms |
468 KB |
Output is correct |
| 8 |
Correct |
1 ms |
468 KB |
Output is correct |
| 9 |
Correct |
1 ms |
468 KB |
Output is correct |
| 10 |
Correct |
1 ms |
468 KB |
Output is correct |
| 11 |
Correct |
1 ms |
452 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
1 ms |
212 KB |
Output is correct |
| 2 |
Correct |
1 ms |
340 KB |
Output is correct |
| 3 |
Correct |
1 ms |
340 KB |
Output is correct |
| 4 |
Correct |
1 ms |
592 KB |
Output is correct |
| 5 |
Correct |
1 ms |
468 KB |
Output is correct |
| 6 |
Correct |
1 ms |
468 KB |
Output is correct |
| 7 |
Correct |
1 ms |
468 KB |
Output is correct |
| 8 |
Correct |
1 ms |
468 KB |
Output is correct |
| 9 |
Correct |
1 ms |
468 KB |
Output is correct |
| 10 |
Correct |
1 ms |
468 KB |
Output is correct |
| 11 |
Correct |
1 ms |
452 KB |
Output is correct |
| 12 |
Correct |
1 ms |
1108 KB |
Output is correct |
| 13 |
Correct |
1 ms |
1108 KB |
Output is correct |
| 14 |
Correct |
1 ms |
1108 KB |
Output is correct |
| 15 |
Correct |
1 ms |
1108 KB |
Output is correct |
| 16 |
Correct |
1 ms |
1108 KB |
Output is correct |
| 17 |
Correct |
1 ms |
1108 KB |
Output is correct |
| 18 |
Correct |
1 ms |
980 KB |
Output is correct |
| 19 |
Correct |
1 ms |
1108 KB |
Output is correct |
| 20 |
Correct |
1 ms |
1092 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
1 ms |
212 KB |
Output is correct |
| 2 |
Correct |
1 ms |
340 KB |
Output is correct |
| 3 |
Correct |
1 ms |
340 KB |
Output is correct |
| 4 |
Correct |
1 ms |
592 KB |
Output is correct |
| 5 |
Correct |
1 ms |
468 KB |
Output is correct |
| 6 |
Correct |
1 ms |
468 KB |
Output is correct |
| 7 |
Correct |
1 ms |
468 KB |
Output is correct |
| 8 |
Correct |
1 ms |
468 KB |
Output is correct |
| 9 |
Correct |
1 ms |
468 KB |
Output is correct |
| 10 |
Correct |
1 ms |
468 KB |
Output is correct |
| 11 |
Correct |
1 ms |
452 KB |
Output is correct |
| 12 |
Correct |
1 ms |
1108 KB |
Output is correct |
| 13 |
Correct |
1 ms |
1108 KB |
Output is correct |
| 14 |
Correct |
1 ms |
1108 KB |
Output is correct |
| 15 |
Correct |
1 ms |
1108 KB |
Output is correct |
| 16 |
Correct |
1 ms |
1108 KB |
Output is correct |
| 17 |
Correct |
1 ms |
1108 KB |
Output is correct |
| 18 |
Correct |
1 ms |
980 KB |
Output is correct |
| 19 |
Correct |
1 ms |
1108 KB |
Output is correct |
| 20 |
Correct |
1 ms |
1092 KB |
Output is correct |
| 21 |
Correct |
2 ms |
3268 KB |
Output is correct |
| 22 |
Correct |
2 ms |
3516 KB |
Output is correct |
| 23 |
Correct |
2 ms |
3916 KB |
Output is correct |
| 24 |
Correct |
9 ms |
12244 KB |
Output is correct |
| 25 |
Correct |
8 ms |
12228 KB |
Output is correct |
| 26 |
Correct |
8 ms |
12244 KB |
Output is correct |
| 27 |
Correct |
8 ms |
12096 KB |
Output is correct |
| 28 |
Correct |
7 ms |
8532 KB |
Output is correct |
