[leetcode] Subsets

public class Solution {    List<List<Integer>> ret=new ArrayList<List<Integer>>();    public List<List<Integer>> subsets(int[] nums) {        Arrays.sort(nums);        List<Integer> list=new ArrayList<Integer>();        sub(list,nums,0,nums.length);        return ret;    }    private void sub(List list,int[] nums,int k,int len){        if(k==len)            ret.add(list);        else{            sub(list,nums,k+1,len);            List<Integer> tlist=new ArrayList<Integer>();            tlist.addAll(list);            tlist.add(nums[k]);            sub(tlist,nums,k+1,len);        }        }}