#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int N = 2005;
const int MOD = 1e9 + 7;
int dp[N][N];
int madd(int x, int y) {
if ((x += y) >= MOD)
x -= MOD;
return x;
}
int mmul(int x, int y) {
return ll(x) * y % MOD;
}
int main() {
cin.tie(0)->sync_with_stdio(0);
int n, s, t; cin >> n >> s >> t;
for (int i = 1; i <= n; i++)
for (int j = 1; j <= i; j++) {
if (i == s || i == t)
dp[i][j] = madd(dp[i - 1][j - 1], dp[i - 1][j]);
else dp[i][j] = madd(mmul(dp[i - 1][j + 1], j),
mmul(dp[i - 1][j - 1], j - (i > s) - (i > t)));
}
cout << dp[n][1] << '\n';
}
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Incorrect |
1 ms |
384 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Incorrect |
1 ms |
384 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Incorrect |
1 ms |
384 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |
# |
Verdict |
Execution time |
Memory |
Grader output |
1 |
Incorrect |
1 ms |
384 KB |
Output isn't correct |
2 |
Halted |
0 ms |
0 KB |
- |