# Gnerate all possible subsets – Subsets

Medium

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.

Implementation

```class Solution {
public List<List<Integer>> subsets(int[] nums) {
List<List<Integer>> result = new ArrayList<>();
if(nums == null || nums.length == 0){
return result;
}
List<Integer> current = new ArrayList<>();
generateSubSets(nums, result, current, 0);
return result;
}

private void generateSubSets(int[] nums, List<List<Integer>> result,
List<Integer> current, int start){
for(int i = start ; i < nums.length ; i++){
int cur = nums[i];
generateSubSets(nums, result, current, i+1);
current.remove(current.size()-1);
}
}
}
```

Complexity Analysis

• Time Complexity: `O(N × 2N)`. 2N to generate all subsets and then `O(N)` to copy each set into output list.
• Space Complexity: `O(N × 2N)`  to keep all the subsets of length  N, since each of N elements could be present or absent.

Categories: Backtracking

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