Subsets

题目：

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],
  []
]

代码如下：

    void getsubset(vector<vector<int> > & result,vector<int> &S,int &i)
    {
        int n=S.size();
        vector<int> tmp;
        for(int j=0;j<n;j++)
        {
            if(i&(1<<j))
            {
                tmp.push_back(S[j]);
            }
        }
        result.push_back(tmp);
    }
    vector<vector<int> > subsets(vector<int> &S)
    {
        int n=S.size();
        sort(S.begin(),S.end());
        vector<vector<int> > result;
        for(int i=0;i<(1<<n);i++)
        {
            getsubset(result,S,i);
        }
        return result;
    }