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],
  []
]

AC code:

class Solution {
public:
    vector<vector<int>> subsets(vector<int>& nums) {
        vector<vector<int>> res;
        vector<int> temp;
        int len = nums.size();
        solve_subset(0, len, res, temp, nums);
        return res;
    }
    void solve_subset(int begin, int n, vector<vector<int>>& res, vector<int>& temp, vector<int>& nums) {
        res.push_back(temp);
        for (int i = begin; i < n; ++i) {
            temp.push_back(nums[i]);
            solve_subset(i+1, n, res, temp, nums);
            temp.pop_back();
        }
    }
};

Runtime: 4 ms, faster than 100.00% of C++ online submissions for Subsets.