Leetcode: Subsets

Given a set of distinct integers, S, return all possible subsets.

Note:

• Elements in a subset must be in non-descending order.
• The solution set must not contain duplicate subsets.

For example,
If S = [1,2,3], a solution is:

[
  [3],
  [1],
  [2],
  [1,2,3],
  [1,3],
  [2,3],
  [1,2],
  []
]

Understand the problem:
As described in the problem, given a set of DISTINCT integers, S, return all possible subsets. Elements in a subset must be in non-descending order. The solution set must not contain duplicate subsets. 


Recursive Solution:

?

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27

public class Solution {     public ArrayList<ArrayList<Integer>> subsets(int[] S) {         ArrayList<ArrayList<Integer>> result = new ArrayList<ArrayList<Integer>>();         if (S == null || S.length == 0) return result;                   Arrays.sort(S);                   result.add(new ArrayList<Integer>());                   ArrayList<Integer> temp = new ArrayList<Integer>();         subsetsHelper(S, 0, result, temp);                   return result;     }           private void subsetsHelper(int[] S, int start, ArrayList<ArrayList<Integer>> result, ArrayList<Integer> temp) {         if (start >= S.length) return;                   for (int i = start; i < S.length; i++) {             temp.add(S[i]);             result.add(new ArrayList<Integer>(temp));             subsetsHelper(S, i + 1, result, temp);                           temp.remove(temp.size() - 1);         }     } }