Subsets II

Given a collection of integers that might contain duplicates, 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 = [1,2,2], a solution is:

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

思路
在上一题的基础上，因为数组元素可能有重复，所以在递归的时候要避免如果有几个相同的元素，在这几个元素中间选择时只能往上增加，不能跳跃的选择。因此增加第24行到第29行的判断。
 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         if(tmp.empty())
25             getSubsets(S, start+1, end);
26         else{
27             if(S[start] > tmp[tmp.size()-1])
28                 getSubsets(S, start+1, end);
29         }
30         tmp.push_back(S[start]);
31         getSubsets(S, start+1, end);
32         tmp.pop_back();
33     }
34     vector<vector<int> > subsetsWithDup(vector<int> &S) {
35         // Note: The Solution object is instantiated only once and is reused by each test case.
36         int n = S.size();
37         initialize(S);
38         getSubsets(S, 0, n);
39         return result;
40     }


 


 






        

        

            posted on 
2013-10-15 10:40 
waruzhi 
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