The n-queens puzzle is the problem of placing n queens on a (n×n) chessboard such that no two queens can attack each other.
Given an integer n, find all distinct solutions to the n-queens puzzle. Each solution contains distinct board configurations of the n-queens’ placement, where the solutions are a permutation of [1,2,3..n] in increasing order, here the number in the ith place denotes that the ith-column queen is placed in the row with that number. For eg below figure represents a chessboard [3 1 4 2].

Example 1:

Input: 1
Output: [1]
Explaination: Only one queen can be placed 
in the single cell available.

Example 2:

Input: 4
Output: [2 4 1 3 ] [3 1 4 2 ]
Explaination: These are the 2 possible solutions.

Your Task:
You do not need to read input or print anything. Your task is to complete the function nQueen() which takes n as input parameter and returns a list containing all the possible chessboard configurations. Return an empty list if no solution exists.

Expected Time Complexity: O(n!)
Expected Auxiliary Space: O(n²) 

Constraints:
1 ≤ n ≤ 10