52. 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 the number of distinct solutions to the n-queens puzzle.
Example 1:
Input: n = 4 Output: 2 Explanation: There are two distinct solutions to the 4-queens puzzle as shown.
Example 2:
Input: n = 1 Output: 1
1 <= n <= 9