leetcode--Subsets II

Given a collection of integers that might contain duplicates, nums, 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 nums = [1,2,2], a solution is:

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

[java]  view plain  copy

1. public class Solution {  
2.     public List<List<Integer>> subsetsWithDup(int[] nums) {  
3.         List<List<Integer>> res = new ArrayList<List<Integer>>();    
4.         if(nums.length==0) return res;    
5.         Arrays.sort(nums);    
6.         helper(nums, 0, new ArrayList<Integer>(), res);    
7.         return res;    
8.     }    
9.         
10.     public void helper(int[] nums, int level, List<Integer> item, List<List<Integer>> res)  {      
11.         res.add(new ArrayList<Integer>(item));    
12.         for(int i=level;i<nums.length;i++){    
13.             item.add(nums[i]);      
14.             helper(nums,i+1,item,res);      
15.             item.remove(item.size()-1);  
16.             //跳过相同的元素    
17.             while(i<(nums.length-1)&&nums[i]==nums[i+1]) {    
18.                 i++;    
19.             }    
20.         }       
21.     }    
22. }  

原文链接http://blog.youkuaiyun.com/crazy__chen/article/details/46434415