LeetCode 78. Subsets

Question

Given an integer array nums of unique elements, return all possible subsets (the power set).

The solution set must not contain duplicate subsets. Return the solution in any order.

https://leetcode.com/problems/subsets/

• Solution1

public List<List<Integer>> subsets(int[] nums) {
    List<List<Integer>> res = new ArrayList<>();
    //Arrays.sort(nums); 不重复没必要sort
    backtrack(res, new ArrayList<>(), nums, 0);
    return res;
}

private void backtrack(List<List<Integer>> list , List<Integer> tempList, int [] nums, int start){
    list.add(new ArrayList<>(tempList));
    for(int i = start; i < nums.length; i++){
        tempList.add(nums[i]);
        backtrack(list, tempList, nums, i + 1);
        tempList.remove(tempList.size() - 1);
    }
}

Complexity:

Time complexity: O(n*2^n)

Space complexity: O(n)