[leetcode]Subsets

Subsets

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],
  []
]

算法思路：

题中要求求出所有的，直接暴力吧，dfs

代码如下：

public class Solution {  List<List<Integer>> res = new ArrayList<List<Integer>>();
    public List<List<Integer>> subsets(int[] s) {
        if(s == null || s.length== 0) return res;
        Arrays.sort(s);
        List<Integer> list = new ArrayList<Integer>();
        dfs(list,0,0,s);
        return res;
    }
    private void dfs(List<Integer> list,int k,int count,int[] s){
        if(count > s.length) return;
        if(count <= s.length){
            res.add(new ArrayList<Integer>(list));
        }
        for(int i = k; i < s.length; i++){
            list.add(s[i]);
            dfs(list,i + 1,count+1,s);
            list.remove(list.size() - 1);
        }
    }
    
}