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.
**Example 1:**
```
Input: nums = [1,2,3]
Output: [[],[1],[2],[1,2],[3],[1,3],[2,3],[1,2,3]]
```
**Example 2:**
```
Input: nums = [0]
Output: [[],[0]]
```