N-Queens Solver

The N-Queens puzzle is the problem of placing N chess queens on an N×N chessboard so that no two queens threaten each other. Given an integer N, return all distinct solutions to the N-Queens puzzle in a list of lists. Each sub-list represents one solution, where 'Q' denotes a queen and '.' denotes an empty space. Input Format: - A single integer N. Output Format: - Print each solution as a list of strings, each string representing a row of the chessboard. Example: Input: 4 Output: ['.Q..', '...Q', 'Q...', '..Q.'] ['..Q.', 'Q...', '...Q', '.Q..']