leetcode------Subsets

标题：	Subsets
通过率：	28.2%
难度：	中等

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

[

  [3],

  [1],

  [2],

  [1,2,3],

  [1,3],

  [2,3],

  [1,2],

  []

]

本题思路就是找出所有子集，具体看代码：

 1 public class Solution {

 2     public ArrayList<ArrayList<Integer>> subsets(int[] S) {

 3         ArrayList<ArrayList<Integer>> res=new ArrayList<ArrayList<Integer>>();

 4         ArrayList<Integer> tmp=new ArrayList<Integer>();

 5         int[]num=S;

 6         Arrays.sort(num);

 7         dfs(res,tmp,0,num);

 8         return res;

 9     }

10     public void dfs(ArrayList<ArrayList<Integer>> res,ArrayList<Integer> tmp,int start,int[] num){

11         if(!res.contains(tmp))

12             res.add(new ArrayList<Integer>(tmp));

13         for(int i=start;i<num.length;i++){

14             tmp.add(num[i]);

15             dfs(res,tmp,i+1,num);

16             tmp.remove(tmp.size()-1);

17         }

18     }

19 }