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.

Example:

Input: nums = [1,2,3]
Output:
[
  [3],
  [1],
  [2],
  [1,2,3],
  [1,3],
  [2,3],
  [1,2],
  []
]
C++：

class Solution {
public:
    void process(vector<int>& nums, vector<int>& path, int index, vector<vector<int> >&result){
        //终止条件，路径保存
        if (index == nums.size()){
            result.push_back(path);
            return;
        }
        process(nums, path, index+1, result);
        path.push_back(nums[index]);
        process(nums, path, index + 1, result);
        //恢复上一级的path
        path.pop_back();
    }

    vector<vector<int>> subsets(vector<int>& nums) {
        sort(nums.begin(), nums.end());
        vector<vector<int> > result;
        vector<int> path;
        process(nums, path, 0, result);
        return result;    
    }
};