<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 {
    int ans;
public:
    void calc(vector<vector<bool>> visited, int itr, int n){
        for(int k=0;k<n;k++){
            if(!visited[itr][k]){
                if(itr==n-1){
                    ans++;
                    // cout<<"ans:"<<itr<<" "<<k<<endl;
                }
                else{
                    vector<vector<bool>> temp=visited;
                    int i=itr+1;
                    int j=k;
                    while(i<n){  //south
                        temp[i][j]=1;
                        i++;
                    } 
                    i=itr+1;
                    j=k+1;
                    while(i<n && j<n){ //south east
                        temp[i][j]=true;
                        i++;
                        j++;
                    }
                    i=itr;
                    j=k;
                    while(i<n && j>=0){ //south west
                        temp[i][j]=true;
                        i++;
                        j--;
                    }
                    // cout<<itr<<" "<<k<<endl;
                    // for(int f=0;f<n;f++){
                    //     for(int g=0;g<n;g++){
                    //         cout<<temp[f][g]<<" ";
                    //     }cout<<endl;
                    // }
                    calc(temp,itr+1,n);
                }
            }
        }
    }
    int totalNQueens(int n) {
        ans=0;
        vector<bool> ele(n,0);
        vector<vector<bool>> visited(n,ele);
        calc(visited,0,n);
        return ans;
    }
};
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