N皇后问题

#include<iostream>
#include<cmath>
using namespace std;
int N;
int a[20];
int num = 0;
int check(int n,int i)
{
for (int j = 1; j < n; j++)
{
if (a[j] == i || abs(a[j] - i) == abs(j-n))
{
return 0;
}
}
return 1;
}
void NQueen(int n)
{
if (n > N)
{
cout <<"第"<< ++num<<"个皇后"<< endl;
for (int i = 1; i <= N; i++)
{
cout << a[i] << " ";
}
cout << endl;
for (int i = 1; i <= N*N; i++)
{
int num = i%N;
int data = i / N+1;
int j = 1;
for (; j <= N; j++)
{
if (num==j && data==a[j])
{
cout << "●";
break;
}
else if (num == 0 && data-1 == a[N])
{
cout << "●";
break;
}
}


if (j == N+1)
{
cout << "○";
}
if (num == 0)
{
cout << endl;
}
}
return;
}
else
{
for (int i = 1; i <= N; i++)
{
if (check(n,i))
{
a[n] = i;
NQueen(n + 1);
}
}
}
}
int  main()
{
cin >> N;
NQueen(1);
return 0;
}