#include <bits/stdc++.h>
using namespace std;
const int MOD = 1e9+7;
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
int N,cs,cf; cin >> N >> cs >> cf;
if (N > 40) return cout << 0, 0;
--cs, --cf;
long long dp[2][N+1][N][N];
memset(dp, 0, sizeof dp);
dp[0][1][0][0] = dp[1][1][0][0] = 1;
for (int n = 2; n <= N; n++) {
for (int s = 0; s < n; s++) {
for (int f = 0; f < n; f++) {
if (s == f) continue;
// finding dp[0][...]
// 0 = right-to-left
// 1 = left-to-right
dp[0][n][s][f] = dp[1][n][s][f] = 0;
for (int p = s+1; p < n; p++) {
(dp[0][n][s][f] += dp[1][n-1][p-1][f-(f > s)]) %= MOD;
}
for (int p = s-1; p >= 0; p--) {
(dp[1][n][s][f] += dp[0][n-1][p][f-(f > s)]) %= MOD;
}
}
}
}
cout << (dp[0][N][cs][cf] + dp[1][N][cs][cf]) % MOD;
}
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
0 ms |
348 KB |
Output is correct |
2 |
Correct |
1 ms |
348 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
0 ms |
348 KB |
Output is correct |
2 |
Correct |
1 ms |
348 KB |
Output is correct |
3 |
Correct |
1 ms |
604 KB |
Output is correct |
4 |
Correct |
4 ms |
1372 KB |
Output is correct |
5 |
Correct |
2 ms |
1368 KB |
Output is correct |
6 |
Correct |
3 ms |
1372 KB |
Output is correct |
7 |
Correct |
2 ms |
1116 KB |
Output is correct |
8 |
Correct |
2 ms |
1372 KB |
Output is correct |
9 |
Correct |
3 ms |
1372 KB |
Output is correct |
10 |
Correct |
3 ms |
1480 KB |
Output is correct |
11 |
Correct |
3 ms |
1368 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
0 ms |
348 KB |
Output is correct |
2 |
Correct |
1 ms |
348 KB |
Output is correct |
3 |
Correct |
1 ms |
604 KB |
Output is correct |
4 |
Correct |
4 ms |
1372 KB |
Output is correct |
5 |
Correct |
2 ms |
1368 KB |
Output is correct |
6 |
Correct |
3 ms |
1372 KB |
Output is correct |
7 |
Correct |
2 ms |
1116 KB |
Output is correct |
8 |
Correct |
2 ms |
1372 KB |
Output is correct |
9 |
Correct |
3 ms |
1372 KB |
Output is correct |
10 |
Correct |
3 ms |
1480 KB |
Output is correct |
11 |
Correct |
3 ms |
1368 KB |
Output is correct |
12 |
Incorrect |
0 ms |
344 KB |
Output isn't correct |
13 |
Halted |
0 ms |
0 KB |
- |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
0 ms |
348 KB |
Output is correct |
2 |
Correct |
1 ms |
348 KB |
Output is correct |
3 |
Correct |
1 ms |
604 KB |
Output is correct |
4 |
Correct |
4 ms |
1372 KB |
Output is correct |
5 |
Correct |
2 ms |
1368 KB |
Output is correct |
6 |
Correct |
3 ms |
1372 KB |
Output is correct |
7 |
Correct |
2 ms |
1116 KB |
Output is correct |
8 |
Correct |
2 ms |
1372 KB |
Output is correct |
9 |
Correct |
3 ms |
1372 KB |
Output is correct |
10 |
Correct |
3 ms |
1480 KB |
Output is correct |
11 |
Correct |
3 ms |
1368 KB |
Output is correct |
12 |
Incorrect |
0 ms |
344 KB |
Output isn't correct |
13 |
Halted |
0 ms |
0 KB |
- |