#include<bits/stdc++.h>
using namespace std;
const int N=2005;
const int mod=1e9+7;
int n,cs,cf,dp[N][N];
int main()
{
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cin>>n>>cs>>cf;
if(cs>cf) swap(cs,cf);
dp[1][0]=1;
for(int i=1;i<=n;i++)
{
for(int j=0;j<=i;j++)
{
if(i==cs||i==cf)
{
dp[i+1][j]=(dp[i+1][j]+dp[i][j])%mod;
if(j) dp[i+1][j-1]=(dp[i+1][j-1]+1ll*dp[i][j]*j%mod)%mod;
continue;
}
dp[i+1][j+1]=(dp[i+1][j+1]+dp[i][j])%mod;
if(j)
{
dp[i+1][j-1]=(dp[i+1][j-1]+1ll*j*(j-1)%mod*dp[i][j]%mod);
if(i>cs) dp[i+1][j-1]=(dp[i+1][j-1]+1ll*dp[i][j]*j%mod)%mod;
if(i>cf) dp[i+1][j-1]=(dp[i+1][j-1]+1ll*dp[i][j]*j%mod)%mod;
}
}
}
cout<<dp[n][0];
}
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
0 ms |
384 KB |
Output is correct |
2 |
Correct |
0 ms |
384 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
0 ms |
384 KB |
Output is correct |
2 |
Correct |
0 ms |
384 KB |
Output is correct |
3 |
Correct |
1 ms |
384 KB |
Output is correct |
4 |
Correct |
1 ms |
512 KB |
Output is correct |
5 |
Correct |
1 ms |
512 KB |
Output is correct |
6 |
Correct |
1 ms |
512 KB |
Output is correct |
7 |
Correct |
1 ms |
512 KB |
Output is correct |
8 |
Correct |
1 ms |
512 KB |
Output is correct |
9 |
Correct |
1 ms |
512 KB |
Output is correct |
10 |
Correct |
1 ms |
512 KB |
Output is correct |
11 |
Correct |
1 ms |
512 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
0 ms |
384 KB |
Output is correct |
2 |
Correct |
0 ms |
384 KB |
Output is correct |
3 |
Correct |
1 ms |
384 KB |
Output is correct |
4 |
Correct |
1 ms |
512 KB |
Output is correct |
5 |
Correct |
1 ms |
512 KB |
Output is correct |
6 |
Correct |
1 ms |
512 KB |
Output is correct |
7 |
Correct |
1 ms |
512 KB |
Output is correct |
8 |
Correct |
1 ms |
512 KB |
Output is correct |
9 |
Correct |
1 ms |
512 KB |
Output is correct |
10 |
Correct |
1 ms |
512 KB |
Output is correct |
11 |
Correct |
1 ms |
512 KB |
Output is correct |
12 |
Correct |
1 ms |
1152 KB |
Output is correct |
13 |
Correct |
1 ms |
1152 KB |
Output is correct |
14 |
Correct |
1 ms |
1280 KB |
Output is correct |
15 |
Correct |
1 ms |
1280 KB |
Output is correct |
16 |
Correct |
1 ms |
1280 KB |
Output is correct |
17 |
Correct |
1 ms |
1280 KB |
Output is correct |
18 |
Correct |
1 ms |
1152 KB |
Output is correct |
19 |
Correct |
2 ms |
1280 KB |
Output is correct |
20 |
Correct |
2 ms |
1280 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
0 ms |
384 KB |
Output is correct |
2 |
Correct |
0 ms |
384 KB |
Output is correct |
3 |
Correct |
1 ms |
384 KB |
Output is correct |
4 |
Correct |
1 ms |
512 KB |
Output is correct |
5 |
Correct |
1 ms |
512 KB |
Output is correct |
6 |
Correct |
1 ms |
512 KB |
Output is correct |
7 |
Correct |
1 ms |
512 KB |
Output is correct |
8 |
Correct |
1 ms |
512 KB |
Output is correct |
9 |
Correct |
1 ms |
512 KB |
Output is correct |
10 |
Correct |
1 ms |
512 KB |
Output is correct |
11 |
Correct |
1 ms |
512 KB |
Output is correct |
12 |
Correct |
1 ms |
1152 KB |
Output is correct |
13 |
Correct |
1 ms |
1152 KB |
Output is correct |
14 |
Correct |
1 ms |
1280 KB |
Output is correct |
15 |
Correct |
1 ms |
1280 KB |
Output is correct |
16 |
Correct |
1 ms |
1280 KB |
Output is correct |
17 |
Correct |
1 ms |
1280 KB |
Output is correct |
18 |
Correct |
1 ms |
1152 KB |
Output is correct |
19 |
Correct |
2 ms |
1280 KB |
Output is correct |
20 |
Correct |
2 ms |
1280 KB |
Output is correct |
21 |
Correct |
6 ms |
3840 KB |
Output is correct |
22 |
Correct |
6 ms |
4096 KB |
Output is correct |
23 |
Correct |
7 ms |
4480 KB |
Output is correct |
24 |
Correct |
31 ms |
14208 KB |
Output is correct |
25 |
Correct |
34 ms |
14200 KB |
Output is correct |
26 |
Correct |
33 ms |
14200 KB |
Output is correct |
27 |
Correct |
37 ms |
14072 KB |
Output is correct |
28 |
Correct |
22 ms |
10240 KB |
Output is correct |