2020-05-02 78. Subsets Medium

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],  []]

有个我比较无语的地方，就是加上了nums.length == 0 的判断之后，虽然执行时间从1ms变成了0ms，但是成绩从50%到了100%，说明leetcode这个题目的测试数据给的太少了呀

class Solution {

    public List<List<Integer>> subsets(int[] nums) {

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

        if (nums.length == 0) return res;

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

        backtrace(cur, res, nums, 0);

        return res;

    }

    private void backtrace(List<Integer> cur, List<List<Integer>> res, int[] nums, int start) {

        res.add(new ArrayList<>(cur));

        for (int i = start; i < nums.length; i++) {

            cur.add(nums[i]);

            backtrace(cur, res, nums, i + 1);

            cur.remove(cur.size() - 1);

        }

    }

}