78. Subsets（回溯）

 

Given a set of distinct integers, nums, return all possible subsets (the power set).

Note: The solution set must not contain duplicate subsets.

Example:

Input: nums = [1,2,3]
Output:
[
  [3],
  [1],
  [2],
  [1,2,3],
  [1,3],
  [2,3],
  [1,2],
  []
]

 class Solution {

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

     public List<List<Integer>> subsets(int[] nums) {
         Arrays.sort(nums);
         help(new ArrayList<>(), nums, 0);
         return res;
     }
     private void help(List<Integer> temp,int[] nums,int index){
         temp = new ArrayList<>(temp);
         res.add(temp);
         for(int  i= index;i<nums.length;i++){
             temp.add(nums[i]);
             help(temp,nums,i+1);
             temp.remove(temp.size()-1);
         }
     }
 }