[LeetCode]Subsets II

原题链接：http://oj.leetcode.com/problems/subsets-ii/

题意描述：

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],

  []

]

题解：

　　这题是含重复元素的子集生成，简化版本是集合中无重复元素，见http://www.cnblogs.com/codershell/p/3619928.html，

　　我在《子集问题（寻找给定集合的所有子集）》一文中详细分析了子集问题，具体解释不再赘述。

 1 class Solution {

 2 public:

 3     bool isExist(vector<vector<int> > &vv,vector<int> v){

 4         for(int i=0; i<vv.size(); i++)

 5             if(vv[i] == v)

 6                 return true;

 7                 

 8         return false;

 9     }

10     

11     void ss(vector<vector<int> > &vv,int* flag,int n, vector<int> &S, int cur){

12         if(cur == n){

13             vector<int> v;

14             for(int i = 0; i < cur; i++)

15                 if(flag[i])

16                     v.push_back(S[i]);

17             if(!isExist(vv,v))

18                 vv.push_back(v);

19             return;

20         }

21         

22         flag[cur] = 1;                                // 选第 cur 个元素

23         ss(vv,flag,n, S, cur+1);

24         flag[cur] = 0;                                // 不选第 cur 个元素

25         ss(vv,flag,n, S, cur+1);

26     }

27     

28     vector<vector<int> > subsetsWithDup(vector<int> &S) {

29         int *flag = (int *)malloc(sizeof(int) * S.size()) ;

30         

31         vector <vector<int>> array;

32         sort(S.begin(),S.end());

33         ss(array,flag,S.size(),S,0);

34         free(flag);

35         return array;

36     }

37 };

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