<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:

vector<vector<string>> ans;
 void p_t_q(vector<vector<char>>b,int i,int j,int noqn)
 {
    noqn++;
    for(int m=0;m<b.size();m++)
    {
        for(int n=0;n<b.size();n++)
        {
            if(m-n ==i-j)
            b[m][n] = '.';
            else if(m+n == i+j)
            b[m][n] = '.';
            else if(m==i)
            b[m][n]='.';
            else if(n==j)
            b[m][n] = '.';
        }
    }
    b[i][j] = 'Q';
    if(noqn == b.size())
    {
        vector<string>v;
        for(int l=0;l<b.size();l++)
        {
            string str = "";
            for(int k=0;k<b.size();k++)
            {
                str += b[l][k];
            }
            v.push_back(str);
        }
        ans.push_back(v);
        return;
    }
    for(int n=0;n<b.size();n++)
    {
        if(b[i+1][n]=='\0')
        {
            p_t_q(b,i+1,n,noqn);
        }
    }

 }
    vector<vector<string>> solveNQueens(int n) {
        vector<vector<char>> b;
        b.resize(n, vector<char>(n, '\0'));
        int noqn=0;
        for(int i=0;i<n;i++)
        {
            p_t_q(b,0,i,noqn);
        }
        return ans;
    }
};
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