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：

public class Solution {
    public ArrayList<ArrayList<Integer>> subsets(int[] S) {
        ArrayList<ArrayList<Integer>> res=new ArrayList<ArrayList<Integer>>();
        ArrayList<Integer> tmp=new ArrayList<Integer>();
        int[]num=S;
        Arrays.sort(num);
        dfs(res,tmp,0,num);
        return res;
    }
    public void dfs(ArrayList<ArrayList<Integer>> res,ArrayList<Integer> tmp,int start,int[] num){
        if(!res.contains(tmp))
            res.add(new ArrayList<Integer>(tmp));
        for(int i=start;i<num.length;i++){
            tmp.add(num[i]);
            dfs(res,tmp,i+1,num);
            tmp.remove(tmp.size()-1);
        }
    }
}