#include <bits/stdc++.h>
using namespace std;
const int N=2005,MOD=1e9+7;
long long mem[N][N];
int n,a,b;
int main()
{
cin >> n >> a >> b;
mem[1][1]=1;
for(int i=2;i<=n;i++)
{
for(int j=1;j<=i;j++)
{
if(i==a||i==b)
{
mem[i][j]=mem[i-1][j]+mem[i-1][j-1];
if(mem[i][j]>=MOD) mem[i][j]-=MOD;
continue;
}
mem[i][j]=mem[i-1][j-1]*(j-((i>a)+(i>b))); // add a new component
mem[i][j]%=MOD;
mem[i][j]+=mem[i-1][j+1]*j; // combine two existing components;
mem[i][j]%=MOD;
}
}
cout << mem[n][1] << endl;
}
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
5 ms |
376 KB |
Output is correct |
| 2 |
Correct |
5 ms |
376 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
5 ms |
376 KB |
Output is correct |
| 2 |
Correct |
5 ms |
376 KB |
Output is correct |
| 3 |
Correct |
5 ms |
376 KB |
Output is correct |
| 4 |
Correct |
5 ms |
504 KB |
Output is correct |
| 5 |
Correct |
5 ms |
504 KB |
Output is correct |
| 6 |
Correct |
5 ms |
504 KB |
Output is correct |
| 7 |
Correct |
5 ms |
504 KB |
Output is correct |
| 8 |
Correct |
5 ms |
584 KB |
Output is correct |
| 9 |
Correct |
5 ms |
504 KB |
Output is correct |
| 10 |
Correct |
5 ms |
508 KB |
Output is correct |
| 11 |
Correct |
5 ms |
504 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
5 ms |
376 KB |
Output is correct |
| 2 |
Correct |
5 ms |
376 KB |
Output is correct |
| 3 |
Correct |
5 ms |
376 KB |
Output is correct |
| 4 |
Correct |
5 ms |
504 KB |
Output is correct |
| 5 |
Correct |
5 ms |
504 KB |
Output is correct |
| 6 |
Correct |
5 ms |
504 KB |
Output is correct |
| 7 |
Correct |
5 ms |
504 KB |
Output is correct |
| 8 |
Correct |
5 ms |
584 KB |
Output is correct |
| 9 |
Correct |
5 ms |
504 KB |
Output is correct |
| 10 |
Correct |
5 ms |
508 KB |
Output is correct |
| 11 |
Correct |
5 ms |
504 KB |
Output is correct |
| 12 |
Correct |
5 ms |
1272 KB |
Output is correct |
| 13 |
Correct |
6 ms |
1148 KB |
Output is correct |
| 14 |
Correct |
5 ms |
1272 KB |
Output is correct |
| 15 |
Correct |
5 ms |
1272 KB |
Output is correct |
| 16 |
Correct |
5 ms |
1272 KB |
Output is correct |
| 17 |
Correct |
5 ms |
1272 KB |
Output is correct |
| 18 |
Correct |
5 ms |
1144 KB |
Output is correct |
| 19 |
Correct |
5 ms |
1272 KB |
Output is correct |
| 20 |
Correct |
5 ms |
1272 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
5 ms |
376 KB |
Output is correct |
| 2 |
Correct |
5 ms |
376 KB |
Output is correct |
| 3 |
Correct |
5 ms |
376 KB |
Output is correct |
| 4 |
Correct |
5 ms |
504 KB |
Output is correct |
| 5 |
Correct |
5 ms |
504 KB |
Output is correct |
| 6 |
Correct |
5 ms |
504 KB |
Output is correct |
| 7 |
Correct |
5 ms |
504 KB |
Output is correct |
| 8 |
Correct |
5 ms |
584 KB |
Output is correct |
| 9 |
Correct |
5 ms |
504 KB |
Output is correct |
| 10 |
Correct |
5 ms |
508 KB |
Output is correct |
| 11 |
Correct |
5 ms |
504 KB |
Output is correct |
| 12 |
Correct |
5 ms |
1272 KB |
Output is correct |
| 13 |
Correct |
6 ms |
1148 KB |
Output is correct |
| 14 |
Correct |
5 ms |
1272 KB |
Output is correct |
| 15 |
Correct |
5 ms |
1272 KB |
Output is correct |
| 16 |
Correct |
5 ms |
1272 KB |
Output is correct |
| 17 |
Correct |
5 ms |
1272 KB |
Output is correct |
| 18 |
Correct |
5 ms |
1144 KB |
Output is correct |
| 19 |
Correct |
5 ms |
1272 KB |
Output is correct |
| 20 |
Correct |
5 ms |
1272 KB |
Output is correct |
| 21 |
Correct |
8 ms |
4728 KB |
Output is correct |
| 22 |
Correct |
8 ms |
5112 KB |
Output is correct |
| 23 |
Correct |
8 ms |
5624 KB |
Output is correct |
| 24 |
Correct |
24 ms |
23032 KB |
Output is correct |
| 25 |
Correct |
23 ms |
23032 KB |
Output is correct |
| 26 |
Correct |
26 ms |
23032 KB |
Output is correct |
| 27 |
Correct |
23 ms |
22904 KB |
Output is correct |
| 28 |
Correct |
16 ms |
15224 KB |
Output is correct |
