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# 0078. Subsets

<https://leetcode.com/problems/subsets>

## Description

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]]
```

**Constraints:**

* `1 <= nums.length <= 10`
* `-10 <= nums[i] <= 10`
* All the numbers of `nums` are **unique**.

## ac

```java
class Solution {
    public List<List<Integer>> subsets(int[] nums) {
        List<List<Integer>> res = new ArrayList<List<Integer>>();
        backtrack(nums, 0, res, new ArrayList<Integer>());
        return res;
    }

    private void backtrack(int[] nums, int start, List<List<Integer>> res, List<Integer> note) {
        res.add(new ArrayList<Integer>(note));

        for (int i = start; i < nums.length; i++) {
            note.add(nums[i]);
            backtrack(nums, i + 1, res, note);
            note.remove(note.size() - 1);
        }
    }
}
```