N Queen

#include<bits/stdc++.h>
using namespace std ;

vector<int> queen ;
int n = 4 ;

bool check(int level, int col)
{
    for (int i = 0; i < level; i++)
    {
        int queenCol = queen[i];
        int queenRow = i;

        if ((col == queenCol) or (abs(level - queenRow) == abs(col - queenCol)))
        {
            return false;
        }
    }
    return true;
}

void printsolution()
{
    for(int i = 0 ; i < n ; i++){
        for(int j = 0 ; j < n ; j++)
            cout << (queen[i] == j) << ' ';
        cout << endl ;
    }
    cout << endl << endl;
}

int solve(int level)
{
    if(level == n)
    {
        // because we Have to Place 8 Queen [ NO OTHER CHOICE LEFT ] //
        // thus we must reach level == n ; thus returning 1 as -> ture --> possible

        printsolution();
        return 1 ;
    }

    int ans = 0 ;

    for(int c = 0 ; c < n ; c++)
    {
        if(check(level,c))
        {
            // place
            queen[level] = c ;
            // calculate
            ans += solve(level + 1) ;
            // revert back --> UNDO
            queen[level] = -1 ;
        }
    }

    return ans ;
}

int main()
{
    cin >> n;
    queen = vector<int>(n,-1) ;
    cout << solve(0) << endl ;
}