Given an integer array nums of unique elements, return all possible subsets (the power set).
The solution set must not contain duplicate subsets. Return the solution in any order.
Input: nums = [1,2,3]
Output: [[],[1],[1,2],[1,2,3],[1,3],[2],[2,3],[3]]
Explanation: There are 2³ = 8 subsets of a 3-element set.
Input: nums = [0]
Output: [[],[0]]
1 <= nums.length <= 10-10 <= nums[i] <= 10nums are unique