<p>The <strong>n-queens</strong> puzzle is the problem of placing <code>n</code> queens on an <code>n x n</code> chessboard such that no two queens attack each other.</p>

<p>Given an integer <code>n</code>, return <em>the number of distinct solutions to the&nbsp;<strong>n-queens puzzle</strong></em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/11/13/queens.jpg" style="width: 600px; height: 268px;" />
<pre>
<strong>Input:</strong> n = 4
<strong>Output:</strong> 2
<strong>Explanation:</strong> There are two distinct solutions to the 4-queens puzzle as shown.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> n = 1
<strong>Output:</strong> 1
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= n &lt;= 9</code></li>
</ul>

class Solution {
private:
    void solve(vector<vector<int>> board, int& res, int x, int y, int n)
    {
        int i, j;
        for(i=0; i<n; i++)
        {
            board[i][y] = 1;
            board[x][i] = 1;
            if(x+i < n && y+i < n)
                board[x+i][y+i] = 1;
            if(x-i >= 0  && y+i < n)
                board[x-i][y+i] = 1;
            if(x+i < n && y-i >= 0)
                board[x+i][y-i] = 1;
            if(x-i >= 0 && y-i >= 0)
                board[x-i][y-i] = 1;
        }
        for(i=0; i<n; i++)
        {
            for(j=0; j<n; j++)
                cout << board[i][j] << " ";
            cout << endl;
        }
        cout << endl;
        for(i=x+1; i<n; i++)
        {
            int flag = 0;
            for(j=0; j<n; j++)
            {
                if(board[i][j] == 0 && i == n-1)
                {
                    cout << i << " " << j << " " << board[i][j]<< endl;
                    flag = 1;
                    res++;
                }
                else if(board[i][j] == 0)
                {
                    solve(board, res, i, j, n);
                }
            }
            if(!flag)
                break;
        }
    }

public:
    int totalNQueens(int n) {
        if(n == 1)
            return 1;
        int res = 0, i = 0;
        vector<vector<int>> board;
        for(i=0; i<n; i++)
        {
            vector<vector<int>> board(n, vector<int>(n, 0));
            solve(board, res, 0, i, n);
        }
        return res;
    }
};
19717