问题描述：

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],
  []
]

代码：

vector<vector<int> > Solution::subsets(vector<int> &S)
{
    sort(S.begin(),S.end());
    int vector_length = S.size();
    int subsets_num = 1 << vector_length;
    vector<vector<int> > result;
    for(int i = 0;i < subsets_num;i++)
    {
        vector<int> subset;
        for(int j = 0;j < vector_length;j++)
        {
            if(i & (1 << j))
                subset.push_back(S[j]);
        }
        result.push_back(subset);
    }
    return result;
}

LeetCode:Subsets