<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>> solveNQueens(int n) {
        int* q = (int*)malloc(sizeof(int) * n);
        for(int i=0; i<n; i++) q[i] = -1;
        int solutionsFound = 0;
        vector<vector<string>> result;

        int idx = 0;
        while (idx != -1) {
            while (idx >= 0 && idx < n) {
                bool found = false;
                for (int col = q[idx]+1; col < n; col++) {
                    bool conflict = false;
                    for (int p=0; p<idx; p++) {
                        int pcol = q[p];
                        if (pcol == col || pcol - col == idx - p || col - pcol == idx - p) {
                            conflict = true;
                            break;
                        }
                    }
                    if (!conflict) {
                        q[idx] = col;
                        found = true;
                        break;
                    }
                }
                if (found)
                    idx ++;
                else {
                    q[idx] = -1;
                    idx --; 
                }
                
            }
            if (idx == n) {
                cout << "Solution found(" << ++solutionsFound << "): ";
                vector<string> sol;
                for(int i=0; i<n; i++) {
                    cout << q[i] << " ";
                    string s = "";
                    for(int j=0; j<n; j++) {
                        s += j == q[i] ? "Q" : ".";
                    }
                    sol.push_back(s);
                }
                result.push_back(sol);
                cout << endl;
                idx --;
            }
        }
        return result;
    }
};
10365