A solution using the divide & conquer methodology. Start from an empty list and index -1, for every index "idx" after this index, create a new copy of the current list and add the number at ** idx** to the new copy, and pass on this new copy to the subproblem, which is the sub-array from

**to the end.**

*idx + 1*I'm starting from -1 because that's the case for an empty list.

```
class Solution {
public List<List<Integer>> subsets(int[] nums) {
List<List<Integer>> res = new LinkedList<>();
subsets(nums, -1, new LinkedList<>(), res);
return res;
}
void subsets(int[] nums, int startIdx, List<Integer> parent, List<List<Integer>> res) {
List<Integer> thisList = new LinkedList<>(parent);
if (startIdx != -1) thisList.add(nums[startIdx]);
res.add(thisList);
for (int i = startIdx + 1; i < nums.length; i++) {
subsets(nums, i, thisList, res);
}
}
}
```