N-Queens

The n-queens puzzle is the problem of placing n queens on an n x n chessboard such that no two queens attack each other.

Given an integer n, return all distinct solutions to the n-queens puzzle. You may return the answer in any order.

Each solution contains a distinct board configuration of the n-queens' placement, where 'Q' and '.' both indicate a queen and an empty space, respectively.

Queens can attack horizontally, vertically, and diagonally. Therefore, no two queens can share:

• The same row
• The same column
• The same diagonal (either direction)

The backtracking approach: place queens row by row. For each row, try each column and check if the placement is safe (no conflicts with already-placed queens). If safe, recurse to next row. If all rows filled, we found a solution.