Subsets

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],
  []
]

思路
递归
 1     vector<vector<int> > result;
 2     vector<int> tmp;
 3     void initialize(vector<int> &S){
 4         tmp.clear();
 5         result.clear();
 6         int n = S.size();
 7         int i,j;
 8         int t;
 9         for(i = 0; i < n-1; i++){
10             for(j = 0; j <= n-2-i; j++){
11                 if(S[j] > S[j+1]){
12                     t = S[j];
13                     S[j] = S[j+1];
14                     S[j+1] = t;
15                 }
16             }
17         }
18     }
19     void getSubsets(vector<int> &S, int start, int end){
20         if(end == start){
21             result.push_back(tmp);
22             return;
23         }
24         getSubsets(S, start+1, end);
25         tmp.push_back(S[start]);
26         getSubsets(S, start+1, end);
27         tmp.pop_back();
28     }
29     vector<vector<int> > subsets(vector<int> &S) {
30         // Note: The Solution object is instantiated only once and is reused by each test case.
31         int n = S.size();
32         initialize(S);
33         getSubsets(S, 0, n);
34         return result;
35     }

 

posted on 2013-10-15 10:15  waruzhi  阅读(145)  评论(0)  编辑  收藏  举报

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