#include <bits/stdc++.h>
using namespace std;
const int N = 2005;
#define ll long long
const ll mod = 1e9 + 7;
void sum(ll &a, ll b)
{
a += b;
if (a >= mod)
a -= mod;
}
ll dp[N][N];
int main()
{
ll n, cs, cf;
cin >> n >> cs >> cf;
dp[1][1] = 1;
for (ll i = 1; i <= n; i++)
for (ll j = 1; j <= i; j++)
{
if (i == cs || i == cf)
{
sum(dp[i][j], dp[i - 1][j - 1]);
sum(dp[i][j], dp[i - 1][j]);
continue;
}
sum(dp[i][j], dp[i - 1][j + 1] * j % mod);
sum(dp[i][j], (dp[i - 1][j - 1] * ((j - 2ll) + 1ll * (i < cs) + 1ll * (i < cf))) % mod);
}
cout << dp[n][1];
return 0;
}
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
0 ms |
212 KB |
Output is correct |
2 |
Correct |
1 ms |
308 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
0 ms |
212 KB |
Output is correct |
2 |
Correct |
1 ms |
308 KB |
Output is correct |
3 |
Correct |
0 ms |
340 KB |
Output is correct |
4 |
Correct |
1 ms |
468 KB |
Output is correct |
5 |
Correct |
1 ms |
436 KB |
Output is correct |
6 |
Correct |
0 ms |
468 KB |
Output is correct |
7 |
Correct |
1 ms |
340 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 |
468 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
0 ms |
212 KB |
Output is correct |
2 |
Correct |
1 ms |
308 KB |
Output is correct |
3 |
Correct |
0 ms |
340 KB |
Output is correct |
4 |
Correct |
1 ms |
468 KB |
Output is correct |
5 |
Correct |
1 ms |
436 KB |
Output is correct |
6 |
Correct |
0 ms |
468 KB |
Output is correct |
7 |
Correct |
1 ms |
340 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 |
468 KB |
Output is correct |
12 |
Correct |
1 ms |
1236 KB |
Output is correct |
13 |
Correct |
1 ms |
1108 KB |
Output is correct |
14 |
Correct |
1 ms |
1236 KB |
Output is correct |
15 |
Correct |
1 ms |
1236 KB |
Output is correct |
16 |
Correct |
1 ms |
1236 KB |
Output is correct |
17 |
Correct |
1 ms |
1236 KB |
Output is correct |
18 |
Correct |
1 ms |
1076 KB |
Output is correct |
19 |
Correct |
1 ms |
1236 KB |
Output is correct |
20 |
Correct |
1 ms |
1180 KB |
Output is correct |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Correct |
0 ms |
212 KB |
Output is correct |
2 |
Correct |
1 ms |
308 KB |
Output is correct |
3 |
Correct |
0 ms |
340 KB |
Output is correct |
4 |
Correct |
1 ms |
468 KB |
Output is correct |
5 |
Correct |
1 ms |
436 KB |
Output is correct |
6 |
Correct |
0 ms |
468 KB |
Output is correct |
7 |
Correct |
1 ms |
340 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 |
468 KB |
Output is correct |
12 |
Correct |
1 ms |
1236 KB |
Output is correct |
13 |
Correct |
1 ms |
1108 KB |
Output is correct |
14 |
Correct |
1 ms |
1236 KB |
Output is correct |
15 |
Correct |
1 ms |
1236 KB |
Output is correct |
16 |
Correct |
1 ms |
1236 KB |
Output is correct |
17 |
Correct |
1 ms |
1236 KB |
Output is correct |
18 |
Correct |
1 ms |
1076 KB |
Output is correct |
19 |
Correct |
1 ms |
1236 KB |
Output is correct |
20 |
Correct |
1 ms |
1180 KB |
Output is correct |
21 |
Correct |
5 ms |
4552 KB |
Output is correct |
22 |
Correct |
5 ms |
4932 KB |
Output is correct |
23 |
Correct |
6 ms |
5560 KB |
Output is correct |
24 |
Correct |
30 ms |
22860 KB |
Output is correct |
25 |
Correct |
28 ms |
22924 KB |
Output is correct |
26 |
Correct |
30 ms |
22860 KB |
Output is correct |
27 |
Correct |
29 ms |
22812 KB |
Output is correct |
28 |
Correct |
18 ms |
15060 KB |
Output is correct |