Subsets II

Given a collection of integers that might contain duplicates, S, return all possible subsets.

If S = [1,2,2], a solution is:

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

public class Solution{
public ArrayList<ArrayList<Integer>> subsetsWithDup(int[] num) {
        Arrays.sort(num);
        ArrayList<ArrayList<Integer>> res = new ArrayList<ArrayList<Integer>>();
        res.add(new ArrayList<Integer>());
        if(num.length<=0) return res;
        DFS(num,0,new ArrayList<Integer>(),res);
        return res;
    }
    public void DFS(int []num,int start,ArrayList<Integer>output,ArrayList<ArrayList<Integer>>res ){
        for(int i=start;i<num.length;i++){
            ArrayList<Integer>temp = new ArrayList<Integer>();
            output.add(num[i]);
            temp.addAll(output);
            res.add(temp);
            DFS(num,i+1,output,res);
            output.remove(output.size()-1);
            while(i<num.length-1 && num[i]==num[i+1]){
                i++;
            }
        }
    }
}