N-Queens (#51)
The n-queens puzzle is the problem of placing n chess queens on an n x n chessboard so that no two queens threaten 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.
Company Tags: Google, Microsoft
Core Concept: Backtracking