[LeetCode] 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],
  []
]

利用回溯法求出给定数组的所有不重复子数组。

这个题没有边界条件，所以使用直接使用回溯标准形式即可

class Solution {
public:
    vector<vector<int>> subsets(vector<int>& nums) {
        vector<vector<int>> res;
        vector<int> tmp;
        int idx = 0;
        helper(res, tmp, nums, idx);
        return res;
    }
    
    void helper(vector<vector<int>>& res, vector<int>& tmp, vector<int>& nums, int idx) {
        res.push_back(tmp);
        for (int i = idx; i < nums.size(); i++) {
            tmp.push_back(nums[i]);
            helper(res, tmp, nums, i + 1);
            tmp.pop_back();
        }
    }
};
// 6 ms