腾讯//子集

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],
  []
]

class Solution {
public:
    vector<vector<int>> subsets(vector<int>& nums) {
        vector<vector<int>> res;
        vector<int> out;
        sort(nums.begin(), nums.end());
        getSubsets(nums,0,out,res);
        return res;
    }
    void getSubsets(vector<int> &nums,int pos,vector<int> &out,vector<vector<int>> &res){
        res.push_back(out);
        for(int i = pos; i < nums.size(); i++){
            out.push_back(nums[i]);
            getSubsets(nums,i+1,out,res);
            out.pop_back();
        }
    }
};

class Solution {
public:
    vector<vector<int>> subsets(vector<int>& nums) {
        vector<vector<int>> res(1);
        sort(nums.begin(), nums.end());
        for(int i = 0; i < nums.size(); i++){
            int size = res.size();
            for(int j = 0; j < size; j++){
                res.push_back(res[j]);
                res.back().push_back(nums[i]);
            }
        }
        return res;
    }
};