<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>all distinct solutions to the <strong>n-queens puzzle</strong></em>. You may return the answer in <strong>any order</strong>.</p>

<p>Each solution contains a distinct board configuration of the n-queens&#39; placement, where <code>&#39;Q&#39;</code> and <code>&#39;.&#39;</code> both indicate a queen and an empty space, respectively.</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> [[&quot;.Q..&quot;,&quot;...Q&quot;,&quot;Q...&quot;,&quot;..Q.&quot;],[&quot;..Q.&quot;,&quot;Q...&quot;,&quot;...Q&quot;,&quot;.Q..&quot;]]
<strong>Explanation:</strong> There exist two distinct solutions to the 4-queens puzzle as shown above
</pre>

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

<pre>
<strong>Input:</strong> n = 1
<strong>Output:</strong> [[&quot;Q&quot;]]
</pre>

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

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

class Solution {
public:

    bool QdiagAvailable(vector<string> currConfig, int r,int c, int n)
    {

        if(currConfig[r][c] == 'Q')
        {
            return true;
        }

        int tempr = r, tempc =c;
        while(tempr >= 0 && tempc >=0)
        {
            if(currConfig[tempr][tempc] == 'Q')
            {
                return true;
            }
            tempr--;
            tempc--;

        }

        tempr =r;
        tempc=c;

        while(tempr < n && tempc < n)
        {
            if(currConfig[tempr][tempc] == 'Q')
            {
                return true;
            }
            tempr++;
            tempc++;

        }

        tempr =r;
        tempc=c;

        while(tempr >= 0 && tempc < n)
        {
            if(currConfig[tempr][tempc] == 'Q')
            {
                return true;
            }
            tempr--;
            tempc++;

        }

        tempr =r;
        tempc=c;

        while(tempr < n && tempc >= 0)
        {
            if(currConfig[tempr][tempc] == 'Q')
            {
                return true;
            }
            tempr++;
            tempc--;

        }

        return false;



    }
    void solveNQueens(int n, int colSum, int r, vector<string>& currConfig, vector<vector<string>>& res) {

        if( colSum == pow(2,n) - 1 )
        {
            res.push_back(currConfig);
            
        }

        if(r>=n)
        {
            return;
        }

        for(int c=0; c<n; c++)
        {
            if( (colSum & (1<<c)) == 0 && !QdiagAvailable(currConfig, r,c, n))
            {
                currConfig[r][c] = 'Q';
                solveNQueens(n, colSum |(1<<c), r+1, currConfig, res );
                currConfig[r][c] = '.';
            }
        }

    }
    vector<vector<string>> solveNQueens(int n) {

        string ith="";

        for(int i =0; i<n; i++)
        {
            ith+=".";
        }
        vector<string> currConfig = vector<string>(n, ith);
        vector<vector<string>> res;
        solveNQueens(n, 0, 0, currConfig, res );

        return res;

        
    }
};
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