Subsets------DFS

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

Have you met this question in a real interview? Yes

Example

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

[

[3],

[1],

[2],

[1,2,3],

[1,3],

[2,3],

[1,2],

[]

]

Note

Elements in a subset must be in non-descending order.

The solution set must not contain duplicate subsets.

public class Solution {
public ArrayList<ArrayList<Integer>> subsets(int[] num) {
ArrayList<ArrayList<Integer>> result = new ArrayList<ArrayList<Integer>>();
if(num == null || num.length == 0) {
return result;
}
ArrayList<Integer> list = new ArrayList<Integer>();
Arrays.sort(num);
subsetsHelper(result, list, num, 0);

return result;
}

private void subsetsHelper(ArrayList<ArrayList<Integer>> result,
ArrayList<Integer> list, int[] num, int pos) {

result.add(new ArrayList<Integer>(list));

for (int i = pos; i < num.length; i++) {

list.add(num[i]);
subsetsHelper(result, list, num, i + 1);
list.remove(list.size() - 1);
}
}
}