<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 check(int n,vector<string>&board,int i,int j)
{
    //upper left diag no queen should be present
  int row =i,col=j;
  while(row>-1&& col>-1)
  {
    if(board[row][col]=='Q')
    return 0;
    row--,col--;

  }

  
    // upper righ diag no queen should be prsent
    row =i,col=j;
    while(row>-1&&col<n)
    {
        if(board[row][col]=='Q')
        return 0;
        row--,col++;
    }

    return 1;


}
void find(int row,int n, vector<vector<string>> &ans, vector<string> board,vector<bool>column){
    // base condition
if(row==n){
    ans.push_back(board);
    return;
}
    // put queen at any n position
    for(int j=0;j<n;j++){
        if(column[j]==0&& check(n,board,row,j))
        {
            column[j]=1;
            board[row][j]='Q';
            find(row+1,n,ans,board,column);
            column[j]=0;
            board[row][j]='.';
        }
    }
}
    vector<vector<string>> solveNQueens(int n) {
      vector<vector<string>> ans;
      vector<string> board(n);
      for(int i=0;i<n;i++)
      for(int j=0;j<n;j++)
      board[i].push_back('.');
      vector<bool>column(n,0);

      find(0,n,ans,board,column);
      return ans;
    }
};
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