Backtracking

1// Subsets — include/exclude at every index
2vector<vector<int>> result;
3vector<int> current;
4 
5void backtrack(vector<int>& nums, int start)
6{
7    result.push_back(current);   // record subset at every node
8 
9    for (int i = start; i < (int)nums.size(); i++)
10    {
11        current.push_back(nums[i]);      // choose
12        backtrack(nums, i + 1);           // explore (no reuse)
13        current.pop_back();               // un-choose
14    }
15}
16 
17vector<vector<int>> subsets(vector<int>& nums)
18{
19    backtrack(nums, 0);
20    return result;
21}