[Leetcode] 78. 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],
[]
]

import java.util.ArrayList;
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);
ArrayList<Integer> list = new ArrayList<Integer>();
helper(S, result, list, 0);
return result;
}
private void helper(int[] S, ArrayList<ArrayList<Integer>> result, ArrayList<Integer> list, int start){
result.add(new ArrayList<Integer>(list));
for(int i = start; i < S.length; i++){
list.add(S[i]);
helper(S, result, list, i + 1);
list.remove(list.size() - 1);
}
}
}