<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:
  std::vector<std::vector<std::string>> solveNQueens(int n) {
    std::vector<std::vector<std::string>> answer;
    std::vector<std::vector<int>> temp(n, std::vector<int>(n, 0));
    find(temp, 0, answer, n);
    return answer;
  }
  void find(std::vector<std::vector<int>> temp, int c, std::vector<std::vector<std::string>> &a, int n) {
    if (c == n) {
      std::vector<std::string> v;
      for (int i = 0; i < n; ++i) {
        std::string str;
        for (int k = 0; k < n; ++k) {
          str += temp[i][k] == 2 ? 'Q' : '.';
        }
        v.emplace_back(str);
      }
      a.emplace_back(v);
      return;
    }
    for(int i = 0; i < n; ++i) {
      if (!temp[c][i]) {
        auto t = temp;
        pos(t, i, c, n);
        t[c][i] = 2;
        find(t, c+1, a, n);
      }
    }
  }
  void pos(std::vector<std::vector<int>> &t, int p, int row, int n) {
    for (int i = 0; i < n; ++i) {
      t[row][i] = 1;
      t[i][p] = 1;
      if(i > row) {
        int s = i - row;
        if(p - s >= 0) t[i][p-s] = 1;
        if(p + s < n)  t[i][p+s] = 1;
      }
    }
  }
};
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