N-Queens Problem

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. Example 1: Input: n = 4 Output: [ [".Q..","...Q","Q...","..Q."], ["..Q.","Q...","...Q",".Q.."] ] Explanation: There exist two distinct solutions to the 4-queens puzzle as shown above. Example 2: Input: n = 1 Output: [ ["Q"] ] Constraints: 1 <= n <= 9 Example Input 4