Printing all possible subsets of a list

Question

I have a List of elements (1, 2, 3), and I need to get the superset (powerset) of that list (without repeating elements). So basically I need to create a List of Lists that

Answer 1

In the given solution we iterate over every index and include current and all further elements.

class Solution {
        public List> subsets(int[] nums) {
            List> ans = new ArrayList<>();
            if(nums == null || nums.length ==0){
                return ans;
            }
            Arrays.sort(nums);
            List subset = new ArrayList<>();
            allSubset(nums, ans , subset , 0);
            return ans;
        }
        private void allSubset(int[] nums,List> ans ,List subset , int idx){
            ans.add(new ArrayList<>(subset));
            for(int i = idx; i < nums.length; i++){
                subset.add(nums[i]);
                allSubset(nums, ans , subset , i+1);
                subset.remove(subset.size() - 1);
            }
        }
        
}