<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:
bool check(int n,int row,int col,vector<string>& board)
{
    for (int i=0;i<row;i++)
    {
         if (board[i][col] == 'Q') {
                return false;
            }
    }
    int i=row;
    int j=col;
    while(i>=0&&j>=0)
    {
        if(board[i][j]=='Q')
        {
            return false;
        }
        i--;
        j--;
    }
    i=row,j=col;
    while(i>=0&&j<n)
    {
        if(board[i][j]=='Q')
        {
            return false;
        }
        i--;
        j++;
    }
    return true;
}
void find(int n,int row, vector<bool>col,vector<string>board,int& cnt)
{
    if(row==n)
    {
        cnt++;
        return;
    }
    for(int k=0;k<n;k++)
    {
        if(col[k]==0&&check(n,row,k,board))
        {
            col[k]=true;
            board[row][k]='Q';
            find(n,row+1,col,board,cnt);
            col[k]=false;
            board[row][k]='.';
        }
    }
}
    int totalNQueens(int n) {
        int cnt=0;
        vector<string>board(n,string(n,'.'));
        vector<bool>col(n,false);
        find(n,0,col,board,cnt);
        return cnt;
    }
};
16112