<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:
    void solveNQueensWrapper(int n, vector<string> visited, vector<string> curr, vector<vector<string>>& ans, int currow) {
        if (currow == n) {
            ans.push_back(curr);
        }
        else {
            for (int i = 0; i < n; i++) {
                if (visited[currow][i] != '!') {
                    vector<string> temp = visited;
                    vector<string> tempcur = curr;
                    tempcur[currow][i] = 'Q';
                    for (int j = 0; j < n; j++) {
                        temp[currow][j] = '!';
                        temp[j][i] = '!';
                        if (currow + j < n) {
                            if (i + j < n) temp[currow + j][i + j] = '!';
                            if (i - j >= 0) temp[currow + j][i - j] = '!';
                        }
                        if (currow - j >= 0) {
                            if (i - j >= 0) temp[currow - j][i - j] = '!';
                            if (i + j < n) temp[currow - j][i + j] = '!';
                        }
                    }
                    solveNQueensWrapper(n, temp, tempcur, ans, currow + 1);
                }
            }
        }
    }
    vector<vector<string>> solveNQueens(int n) {
        vector<vector<string>> ans;
        const std::string base(n, '.');
        vector<string> visited(n, base);
        vector<string> cur(n, base);
        solveNQueensWrapper(n, visited, cur, ans, 0);
        return ans;
    }
};
29603