July11_2020.java

// Subset of set - classic DFS problem


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