<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<int>> board;
    int N;
    vector<vector<string>> res;
    void converter(vector<vector<int>> board){
        vector<string> temp;
        for(auto x : board){
            string str = "";
            for(int z : x){
                if(z == 2) str += 'Q';
                else str += '.';
            }
            temp.push_back(str);
        }
        res.push_back(temp);
    }

    void rec(vector<vector<int>> board, int ind){
        if(ind == N){
            converter(board);
            return;
        }
        vector<vector<int>> temp = board;
        for(int i=0; i<N; i++){
            if(board[ind][i] == 0){ // khali
                board[ind][i] = 2;
                for(int j=i+1; j<N; j++) board[ind][j] = 1; // horijontally
                for(int j=ind+1; j<N; j++) board[j][i] = 1; // virtically
                for(int j=1; ind+j<N && i+j<N; j++) board[ind+j][i+j] = 1;
                for(int j=1; ind+j<N && i-j>=0; j++) board[ind+j][i-j] = 1;
                for(int j=1; ind-j>=0 && i+j<N; j++) board[ind-j][i+j] = 1;
                for(int j=1; ind-j>=0 && i-j>=0; j++) board[ind-j][i-j] = 1;
                rec(board, ind+1);
                board = temp;
            }
        }
        
    }
    vector<vector<string>> solveNQueens(int n) {
        res.clear();
        board.clear();
        board.resize(n);
        N = n;
        for(int i=0; i<n; i++) board[i].resize(n);
        rec(board, 0);
        return res;
    }
};
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