78. Subsets

Given a set of distinct integers, nums, return all possible subsets (the power set).

Note: The solution set must not contain duplicate subsets.

For example,
If nums = [1,2,3], a solution is:

[
  [3],
  [1],
  [2],
  [1,2,3],
  [1,3],
  [2,3],
  [1,2],
  []
]

解题思路：

1-n进行递归？

class Solution {
private:
    vector<vector<int>> ret;
    vector<int> store;
    void deep(int level, vector<vector<int>> &ret,vector<int>& nums,int count,int index){
        if(level == 0) {ret.push_back(store);return;}
        if(level == nums.size()) {ret.push_back(nums);return;}
        if(count == level){ret.push_back(store);return;}

        for(int i=index;i<nums.size();i++){
            store.push_back(nums[i]);
            deep(level,ret,nums,count+1,i+1);
            store.pop_back();

        }



    }

public:
    vector<vector<int>> subsets(vector<int>& nums) {


        for(int i=0;i<=nums.size();i++){
            store.clear();
            deep(i,ret,nums,0,0);
        }
        return ret;

    }
};