LeetCode Subsets

 1 public class Solution {
 2     public List<List<Integer>> subsets(int[] nums) {
 3         List<List<Integer>> res = new ArrayList<List<Integer>>();
 4         if(nums == null || nums.length == 0){
 5             return res;
 6         }
 7         //Add [] to res.
 8         res.add(new ArrayList<Integer>());
 9         //non-descending order
10         Arrays.sort(nums);
11         for(int i = 0; i<nums.length; i++){
12             int size = res.size();
13             for(int j = 0; j< size; j++){
14                 //add new element to each element of res
15                 ArrayList<Integer> elem= new ArrayList<Integer>(res.get(j));
16                 elem.add(nums[i]);
17                 res.add(elem);
18             }
19         }
20         return res;
21     }
22 }