leetcode--Subsets

Given a set of distinct integers, 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 = [1,2,3], a solution is:

[  [3],  [1],  [2],  [1,2,3],  [1,3],  [2,3],  [1,2],  []]

[java] view plain copy

1. public class Solution {  
2.     public List<List<Integer>> subsets(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.         }     
17.     }  
18. }  

原文链接http://blog.csdn.net/crazy__chen/article/details/46423523