N-Queens

Problem

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

Given an integer n, return all distinct solutions to the n-queens puzzle.

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

Example

There exist two distinct solutions to the 4-queens puzzle:

[
  // Solution 1
  [".Q..",
    "...Q",
    "Q...",
    "..Q."
  ],
  // Solution 2
  ["..Q.",
    "Q...",
    "...Q",
    ".Q.."
  ]
]

Challenge

Can you do it without recursion?