<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>the number of distinct solutions to the&nbsp;<strong>n-queens puzzle</strong></em>.</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> 2
<strong>Explanation:</strong> There are two distinct solutions to the 4-queens puzzle as shown.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> n = 1
<strong>Output:</strong> 1
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= n &lt;= 9</code></li>
</ul>

class Solution {
public:
void rec(vector<vector<string>>& res,int i,int n,vector<string>& tmp,vector<vector<int>>& pos){
    if(i>=n){
        res.push_back(tmp);
        // cout<<"asda"<<endl;
        return;
    }
    
    for(int j=0;j<n;++j){
        int check=1;
        for(auto it:pos){
            int idx=it[0],jdx=it[1];
            if(j==jdx)check=0;
            if(abs(i-idx)==abs(j-jdx))check=0;   
        }
        if(check==1){
            pos.push_back({i,j});
            tmp[i][j]='Q';
            rec(res,i+1,n,tmp,pos);
            tmp[i][j]='.';
            pos.pop_back();
        }
    }
}
    int totalNQueens(int n) {
        vector<string>tmp;
        vector<vector<int>>pos;
        vector<vector<string>>res;
        string dummy="";
        for(int i=0;i<n;++i){
            dummy+='.';
        }
        for(int i=0;i<n;++i){
            tmp.push_back(dummy);
        }
        rec(res,0,n,tmp,pos);
        return res.size();
    }
};
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