Given a set of distinct integers, S, return all possible subsets.

Note:

• Elements in a subset must be in non-descending order.
• The solution set must not contain duplicate subsets.

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

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

class Solution {
public:
    std::vector<std::vector<int> > subsets(std::vector<int> &S) {
		std::sort(S.begin(),S.end());
		dfs(std::vector<int>(),S,0);
		return result;
    }
private:
	std::vector<std::vector<int>> result;
	void dfs(std::vector<int> vec, std::vector<int> &S, int n)
	{
		if(n == S.size())
		{
			result.push_back(vec);
			return;
		}
		else
		{
			dfs(vec,S,n+1);
			vec.push_back(S[n]);
			dfs(vec,S,n+1);
		}
	}
};

leetcode - Subsets