Given a collection of integers that might contain duplicates, nums, return all possible subsets.
Note: The solution set must not contain duplicate subsets.
For example,
If nums = [1,2,2], a solution is:
[ [2], [1], [1,2,2], [2,2], [1,2], [] ]
此题以前做过类似的题目，不做解释，代码如下：
1 public class Solution { 2 public List<List<Integer>> subsetsWithDup(int[] nums) { 3 List<List<Integer>> res= new ArrayList<>(); 4 Arrays.sort(nums); 5 helper(res,new ArrayList<Integer>(),nums,0); 6 return res; 7 } 8 public void helper(List<List<Integer>> res,List<Integer> list,int[] nums,int index){ 9 if(!res.contains(list)){ 10 res.add(new ArrayList<Integer>(list)); 11 } 12 for(int i=index;i<nums.length;i++){ 13 list.add(nums[i]); 14 helper(res,list,nums,i+1); 15 list.remove(list.size()-1); 16 } 17 return; 18 19 } 20 }
原文：http://www.cnblogs.com/codeskiller/p/6509397.html