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N-Queen Problem
Hard Accuracy: 61.43% Submissions: 1562 Points: 8

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.

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