#include <bits/stdc++.h>
using namespace std;
const int MOD = 1000000007;
int Add(int x, int y) {
return (x + y) % MOD;
}
void Increase(int& x, int y) {
x = Add(x, y);
}
int Multiply(int x, int y) {
return 1LL * x * y % MOD;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int n, startPosition, finishPosition;
cin >> n >> startPosition >> finishPosition;
vector<vector<int>> ways(n + 2, vector<int>(n + 1));
ways[2][1] = 1;
for (int i = 2; i <= n; ++i) {
for (int components = 1; components < i; ++components) {
if (ways[i][components] == 0) {
continue;
}
if (i == startPosition || i == finishPosition) {
Increase(ways[i + 1][components + 1], ways[i][components]); // open a new component on the side
Increase(ways[i + 1][components], ways[i][components]); // append to the side
}
else {
// create a new component
int validPosition = (components + 1) - (i > startPosition) - (i > finishPosition);
Increase(ways[i + 1][components + 1], Multiply(validPosition, ways[i][components]));
// merge two component
validPosition = components - 1;
Increase(ways[i + 1][components - 1], Multiply(validPosition, ways[i][components]));
}
}
}
cout << ways[n + 1][1];
return 0;
}
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
1 ms |
204 KB |
Output is correct |
2 |
Correct |
1 ms |
204 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
1 ms |
204 KB |
Output is correct |
2 |
Correct |
1 ms |
204 KB |
Output is correct |
3 |
Correct |
1 ms |
316 KB |
Output is correct |
4 |
Correct |
1 ms |
204 KB |
Output is correct |
5 |
Correct |
1 ms |
204 KB |
Output is correct |
6 |
Correct |
1 ms |
204 KB |
Output is correct |
7 |
Correct |
1 ms |
204 KB |
Output is correct |
8 |
Correct |
1 ms |
204 KB |
Output is correct |
9 |
Correct |
1 ms |
204 KB |
Output is correct |
10 |
Correct |
1 ms |
204 KB |
Output is correct |
11 |
Correct |
1 ms |
204 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
1 ms |
204 KB |
Output is correct |
2 |
Correct |
1 ms |
204 KB |
Output is correct |
3 |
Correct |
1 ms |
316 KB |
Output is correct |
4 |
Correct |
1 ms |
204 KB |
Output is correct |
5 |
Correct |
1 ms |
204 KB |
Output is correct |
6 |
Correct |
1 ms |
204 KB |
Output is correct |
7 |
Correct |
1 ms |
204 KB |
Output is correct |
8 |
Correct |
1 ms |
204 KB |
Output is correct |
9 |
Correct |
1 ms |
204 KB |
Output is correct |
10 |
Correct |
1 ms |
204 KB |
Output is correct |
11 |
Correct |
1 ms |
204 KB |
Output is correct |
12 |
Correct |
1 ms |
444 KB |
Output is correct |
13 |
Correct |
1 ms |
444 KB |
Output is correct |
14 |
Correct |
1 ms |
460 KB |
Output is correct |
15 |
Correct |
1 ms |
460 KB |
Output is correct |
16 |
Correct |
1 ms |
460 KB |
Output is correct |
17 |
Correct |
1 ms |
460 KB |
Output is correct |
18 |
Correct |
1 ms |
332 KB |
Output is correct |
19 |
Correct |
1 ms |
460 KB |
Output is correct |
20 |
Correct |
1 ms |
460 KB |
Output is correct |
# |
결과 |
실행 시간 |
메모리 |
Grader output |
1 |
Correct |
1 ms |
204 KB |
Output is correct |
2 |
Correct |
1 ms |
204 KB |
Output is correct |
3 |
Correct |
1 ms |
316 KB |
Output is correct |
4 |
Correct |
1 ms |
204 KB |
Output is correct |
5 |
Correct |
1 ms |
204 KB |
Output is correct |
6 |
Correct |
1 ms |
204 KB |
Output is correct |
7 |
Correct |
1 ms |
204 KB |
Output is correct |
8 |
Correct |
1 ms |
204 KB |
Output is correct |
9 |
Correct |
1 ms |
204 KB |
Output is correct |
10 |
Correct |
1 ms |
204 KB |
Output is correct |
11 |
Correct |
1 ms |
204 KB |
Output is correct |
12 |
Correct |
1 ms |
444 KB |
Output is correct |
13 |
Correct |
1 ms |
444 KB |
Output is correct |
14 |
Correct |
1 ms |
460 KB |
Output is correct |
15 |
Correct |
1 ms |
460 KB |
Output is correct |
16 |
Correct |
1 ms |
460 KB |
Output is correct |
17 |
Correct |
1 ms |
460 KB |
Output is correct |
18 |
Correct |
1 ms |
332 KB |
Output is correct |
19 |
Correct |
1 ms |
460 KB |
Output is correct |
20 |
Correct |
1 ms |
460 KB |
Output is correct |
21 |
Correct |
3 ms |
1980 KB |
Output is correct |
22 |
Correct |
4 ms |
2252 KB |
Output is correct |
23 |
Correct |
5 ms |
2500 KB |
Output is correct |
24 |
Correct |
29 ms |
16064 KB |
Output is correct |
25 |
Correct |
26 ms |
16072 KB |
Output is correct |
26 |
Correct |
28 ms |
15948 KB |
Output is correct |
27 |
Correct |
28 ms |
15936 KB |
Output is correct |
28 |
Correct |
17 ms |
9184 KB |
Output is correct |