#include"bits/stdc++.h"
using namespace std;
#define ll long long
#define endl "\n"
#define fastio ios_base::sync_with_stdio(false)
#define inf LLONG_MAX
const ll mod=1e9+7;
const int lmt=2e3+10;
ll dp[lmt][lmt];
int main(){
fastio;
int n,cs,cf;
cin>>n>>cs>>cf;
if(cs>cf) swap(cs,cf);
dp[1][1]=1;
int blok=(1==cs || 1==cf);
for(int i=1;i<n;i++){
if(i+1==cs || i+1==cf) blok++;
for(int j=1;j<=n;j++){
if(i+1==cs || i+1==cf){
dp[i+1][j]=(dp[i+1][j]+dp[i][j])%mod;
dp[i+1][j+1]=(dp[i+1][j+1]+dp[i][j])%mod;
continue;
}
dp[i+1][j+1]=(dp[i+1][j+1]+(dp[i][j]*(j+1-blok))%mod)%mod;
if(j-1>0) dp[i+1][j-1]=(dp[i+1][j-1]+(dp[i][j]*(j-1))%mod)%mod;
}
}
cout<<dp[n][1]<<endl;
return 0;
}
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
1 ms |
332 KB |
Output is correct |
| 2 |
Correct |
1 ms |
332 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
1 ms |
332 KB |
Output is correct |
| 2 |
Correct |
1 ms |
332 KB |
Output is correct |
| 3 |
Correct |
1 ms |
332 KB |
Output is correct |
| 4 |
Correct |
1 ms |
460 KB |
Output is correct |
| 5 |
Correct |
1 ms |
460 KB |
Output is correct |
| 6 |
Correct |
0 ms |
460 KB |
Output is correct |
| 7 |
Correct |
1 ms |
460 KB |
Output is correct |
| 8 |
Correct |
0 ms |
448 KB |
Output is correct |
| 9 |
Correct |
1 ms |
460 KB |
Output is correct |
| 10 |
Correct |
1 ms |
460 KB |
Output is correct |
| 11 |
Correct |
1 ms |
460 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
1 ms |
332 KB |
Output is correct |
| 2 |
Correct |
1 ms |
332 KB |
Output is correct |
| 3 |
Correct |
1 ms |
332 KB |
Output is correct |
| 4 |
Correct |
1 ms |
460 KB |
Output is correct |
| 5 |
Correct |
1 ms |
460 KB |
Output is correct |
| 6 |
Correct |
0 ms |
460 KB |
Output is correct |
| 7 |
Correct |
1 ms |
460 KB |
Output is correct |
| 8 |
Correct |
0 ms |
448 KB |
Output is correct |
| 9 |
Correct |
1 ms |
460 KB |
Output is correct |
| 10 |
Correct |
1 ms |
460 KB |
Output is correct |
| 11 |
Correct |
1 ms |
460 KB |
Output is correct |
| 12 |
Correct |
1 ms |
1356 KB |
Output is correct |
| 13 |
Correct |
1 ms |
1228 KB |
Output is correct |
| 14 |
Correct |
1 ms |
1356 KB |
Output is correct |
| 15 |
Correct |
2 ms |
1356 KB |
Output is correct |
| 16 |
Correct |
1 ms |
1356 KB |
Output is correct |
| 17 |
Correct |
1 ms |
1340 KB |
Output is correct |
| 18 |
Correct |
1 ms |
1228 KB |
Output is correct |
| 19 |
Correct |
1 ms |
1356 KB |
Output is correct |
| 20 |
Correct |
1 ms |
1404 KB |
Output is correct |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
1 ms |
332 KB |
Output is correct |
| 2 |
Correct |
1 ms |
332 KB |
Output is correct |
| 3 |
Correct |
1 ms |
332 KB |
Output is correct |
| 4 |
Correct |
1 ms |
460 KB |
Output is correct |
| 5 |
Correct |
1 ms |
460 KB |
Output is correct |
| 6 |
Correct |
0 ms |
460 KB |
Output is correct |
| 7 |
Correct |
1 ms |
460 KB |
Output is correct |
| 8 |
Correct |
0 ms |
448 KB |
Output is correct |
| 9 |
Correct |
1 ms |
460 KB |
Output is correct |
| 10 |
Correct |
1 ms |
460 KB |
Output is correct |
| 11 |
Correct |
1 ms |
460 KB |
Output is correct |
| 12 |
Correct |
1 ms |
1356 KB |
Output is correct |
| 13 |
Correct |
1 ms |
1228 KB |
Output is correct |
| 14 |
Correct |
1 ms |
1356 KB |
Output is correct |
| 15 |
Correct |
2 ms |
1356 KB |
Output is correct |
| 16 |
Correct |
1 ms |
1356 KB |
Output is correct |
| 17 |
Correct |
1 ms |
1340 KB |
Output is correct |
| 18 |
Correct |
1 ms |
1228 KB |
Output is correct |
| 19 |
Correct |
1 ms |
1356 KB |
Output is correct |
| 20 |
Correct |
1 ms |
1404 KB |
Output is correct |
| 21 |
Correct |
7 ms |
6300 KB |
Output is correct |
| 22 |
Correct |
7 ms |
6860 KB |
Output is correct |
| 23 |
Correct |
11 ms |
7776 KB |
Output is correct |
| 24 |
Correct |
44 ms |
31728 KB |
Output is correct |
| 25 |
Correct |
45 ms |
31692 KB |
Output is correct |
| 26 |
Correct |
41 ms |
31856 KB |
Output is correct |
| 27 |
Correct |
42 ms |
31556 KB |
Output is correct |
| 28 |
Correct |
28 ms |
23820 KB |
Output is correct |
