#include<bits/stdc++.h>
#define mod 1000000007
using namespace std;
typedef long long ll;
int n, a, b;
inline int add(int a, int b)
{
if(!b)
return a;
int x = a+b;
if(x >= mod)
x -= mod;
else
if(x < 0)
x += mod;
return x;
}
ll mul(ll a, ll b)
{
return (a * b) % mod;
}
ll dp[2002][2002];
int main()
{
cin >> n >> a >> b;
dp[1][1] = 1;
for(int i = 2; i <= n; ++i)
for(int j = 1; j <= n; ++j)
{
if(i == a || i == b)
dp[i][j] = add(dp[i-1][j-1], dp[i-1][j]);
else
dp[i][j] = add(mul(dp[i-1][j+1], j), mul(dp[i-1][j-1], j - (i > a) - (i > b)));
}
cout << dp[n][1];
return 0;
}
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
5 ms |
380 KB |
Output is correct |
| 2 |
Correct |
5 ms |
376 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
5 ms |
380 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 |
504 KB |
Output is correct |
| 9 |
Correct |
5 ms |
504 KB |
Output is correct |
| 10 |
Correct |
5 ms |
504 KB |
Output is correct |
| 11 |
Correct |
5 ms |
504 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
5 ms |
380 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 |
504 KB |
Output is correct |
| 9 |
Correct |
5 ms |
504 KB |
Output is correct |
| 10 |
Correct |
5 ms |
504 KB |
Output is correct |
| 11 |
Correct |
5 ms |
504 KB |
Output is correct |
| 12 |
Correct |
6 ms |
1400 KB |
Output is correct |
| 13 |
Correct |
5 ms |
1272 KB |
Output is correct |
| 14 |
Correct |
6 ms |
1400 KB |
Output is correct |
| 15 |
Correct |
5 ms |
1400 KB |
Output is correct |
| 16 |
Correct |
5 ms |
1400 KB |
Output is correct |
| 17 |
Correct |
5 ms |
1400 KB |
Output is correct |
| 18 |
Correct |
5 ms |
1276 KB |
Output is correct |
| 19 |
Correct |
6 ms |
1400 KB |
Output is correct |
| 20 |
Correct |
6 ms |
1400 KB |
Output is correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
5 ms |
380 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 |
504 KB |
Output is correct |
| 9 |
Correct |
5 ms |
504 KB |
Output is correct |
| 10 |
Correct |
5 ms |
504 KB |
Output is correct |
| 11 |
Correct |
5 ms |
504 KB |
Output is correct |
| 12 |
Correct |
6 ms |
1400 KB |
Output is correct |
| 13 |
Correct |
5 ms |
1272 KB |
Output is correct |
| 14 |
Correct |
6 ms |
1400 KB |
Output is correct |
| 15 |
Correct |
5 ms |
1400 KB |
Output is correct |
| 16 |
Correct |
5 ms |
1400 KB |
Output is correct |
| 17 |
Correct |
5 ms |
1400 KB |
Output is correct |
| 18 |
Correct |
5 ms |
1276 KB |
Output is correct |
| 19 |
Correct |
6 ms |
1400 KB |
Output is correct |
| 20 |
Correct |
6 ms |
1400 KB |
Output is correct |
| 21 |
Correct |
10 ms |
6392 KB |
Output is correct |
| 22 |
Correct |
11 ms |
7032 KB |
Output is correct |
| 23 |
Correct |
14 ms |
7800 KB |
Output is correct |
| 24 |
Correct |
46 ms |
31608 KB |
Output is correct |
| 25 |
Correct |
44 ms |
31480 KB |
Output is correct |
| 26 |
Correct |
46 ms |
31608 KB |
Output is correct |
| 27 |
Correct |
44 ms |
31480 KB |
Output is correct |
| 28 |
Correct |
29 ms |
23800 KB |
Output is correct |
