#include<bits/stdc++.h>
#define mod 1000000007
using namespace std;
int n, a, b;
int add(int a, int b)
{
int x = a+b;
if(x >= mod)
x -= mod;
if(x < 0)
x += mod;
return x;
}
int dp[2][202][202][202];
int main()
{
cin >> n >> a >> b;
for(int i = 1; i <= n; ++i)
if(i != a && i != b)
dp[(a < i)][i - 1 - (a < i)][n - i - (a > i)][b - (a < b) - (i < b)] = 1;
int ans = 0;
for(int sum = n-2; sum >= 1; --sum)
{
for(int i = 0; i <= sum; ++i)
for(int pos = 1; pos <= sum; ++pos)
{
int smaller = i;
int bigger = sum - i;
// cout << sum << '\n';
// cout << smaller << " " << bigger << " " << pos << '\n';
// cout << dp[0][smaller][bigger][pos] << " " << dp[1][smaller][bigger][pos] << '\n';
if(sum == 1)
{
ans = add(ans, dp[0][smaller][bigger][1]);
ans = add(ans, dp[1][smaller][bigger][1]);
}
else
for(int relpos = 1; relpos <= sum; ++relpos)
{
if(pos == relpos)
continue;
if(relpos <= smaller)
dp[0][relpos - 1][sum - relpos][pos - (relpos < pos)] = add(dp[0][relpos - 1][sum - relpos][pos - (relpos < pos)],
dp[1][smaller][bigger][pos]);
else
dp[1][relpos - 1][sum - relpos][pos - (relpos < pos)] = add(dp[1][relpos - 1][sum - relpos][pos - (relpos < pos)],
dp[0][smaller][bigger][pos]);
}
}
}
cout << ans;
return 0;
}
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
5 ms |
376 KB |
Output is correct |
| 2 |
Incorrect |
5 ms |
376 KB |
Output isn't correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
5 ms |
376 KB |
Output is correct |
| 2 |
Incorrect |
5 ms |
376 KB |
Output isn't correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
5 ms |
376 KB |
Output is correct |
| 2 |
Incorrect |
5 ms |
376 KB |
Output isn't correct |
| # |
Verdict |
Execution time |
Memory |
Grader output |
| 1 |
Correct |
5 ms |
376 KB |
Output is correct |
| 2 |
Incorrect |
5 ms |
376 KB |
Output isn't correct |
