[C++] 15918 - 랭퍼든 수열쟁이야!!

문제 링크 : https://www.acmicpc.net/problem/15918

15918번: 랭퍼든 수열쟁이야!!

 

 

#include<bits/stdc++.h>
 
using namespace std;
 
#define endl '\n';
 
int A[25];
bool isuse[15];
int cnt;
 
int N, X, Y;
 
void R(int x)
{
    if(x == 2*N)
    {
        cnt++;
        return;
    }
 
    if(A[x] == 0)
    {
        for(int i = 1; i <= N; ++i)
        {
            if(isuse[i] == 0 && x+i+1 <= 2*N && A[x+i+1] == 0)
            {
                A[x] = A[x+i+1] = i;
                isuse[i] = 1;
                R(x+1);
                isuse[i] = 0;
                A[x] = A[x+i+1] = 0;
            }
        }
    }
    else
        R(x+1);
}
 
int main(void)
{
    int i;
    cin >> N >> X >> Y;
 
    isuse[Y-X-1] = 1;
    A[X] = A[Y] = Y-X-1;
 
    R(1);
 
    cout << cnt;
 
    return 0;
}