Subsets <leetcode>

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],
  []
]

算法:该题的解空间类似一个排列树，但是又不完全相同，树种根到所有节点的路径是一个解，还有不要忘了空集。直接用深度优先遍历解决：

10/10test cases passed
Runtime::44ms

 1 class Solution {
 2 public:
 3     vector<vector<int> > subsets(vector<int> &S) {
 4        vector<vector<int>> result;
 5        int len=S.size();
 6        if(S.size()<=0)  return result;
 7         sort(S.begin(),S.end());
 8         vector<int>  temp;
 9         doit(result,S,0,len,temp);
10         return result;
11     }
12     void doit(vector<vector<int>> &result,vector<int> &s,int dep,int len,vector<int> &temp)
13     {
14         result.push_back(temp);
15         for(int i=dep;i<len;i++)
16         {
17             temp.push_back(s[i]);
18             doit(result,s,i+1,len,temp);
19             temp.pop_back();
20         }
21     }
22 };