给定一组不含重复元素的整数数组 nums，返回该数组所有可能的子集（幂集）。说明：解集不能包含重复的子集。示例:输入: nums = [1,2,3]输出:[  [3],  [1],  [2],  [1,2,3],  [1,3],  [2,3],  [1,2],  []]

function backtrack(list, tempList, nums, start) {  list.push([...tempList]);  for (let i = start; i < nums.length; i++) {    tempList.push(nums[i]);    backtrack(list, tempList, nums, i + 1);    tempList.pop();  }}/** * @param {number[]} nums * @return {number[][]} */var subsets = function (nums) {  const list = [];  backtrack(list, [], nums, 0);  return list;};

class Solution {public:    vector<vector<int>> subsets(vector<int>& nums) {        auto ret = vector<vector<int>>();        auto tmp = vector<int>();        backtrack(ret, tmp, nums, 0);        return ret;    }    void backtrack(vector<vector<int>>& list, vector<int>& tempList, vector<int>& nums, int start) {        list.push_back(tempList);        for (auto i = start; i < nums.size(); ++i) {            tempList.push_back(nums[i]);            backtrack(list, tempList, nums, i + 1);            tempList.pop_back();        }    }};

class Solution {    // 结果    List<List<Integer>> res = new ArrayList();    public List<List<Integer>> subsets(int[] nums) {        backtrack(nums, 0, new ArrayList<Integer>());        return res;    }    public void backtrack(int[] nums, int start, ArrayList<Integer> track)    {        // 注意：深拷贝        res.add(new ArrayList(track));        for(int i=start; i<nums.length;i++)        {            // 做选择            track.add(nums[i]);            // 回溯            backtrack(nums, i+1, track);            // 撤销选择            track.remove(track.size()-1);        }    }}

class Solution:    def subsets(self, nums):        self.res = []        self.track = []        self.backtrack(nums, 0, self.track)        return self.res    def backtrack(self, nums, start, track):        # 注意深拷贝        self.res.append(list(self.track))        for i in range(start, len(nums)):            # 做选择            self.track.append(nums[i])            # 回溯            self.backtrack(nums, i+1, self.track)            # 撤销选择            self.track.pop()