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);
        }
    }
}