标签：des style blog color 使用 os io strong
Given a collection of integers that might contain duplicates, S, return all possible subsets.
Note:
For example,
If S = [1,2,2], a solution is:
[
[2],
[1],
[1,2,2],
[2,2],
[1,2],
[]
]
思路：先对输入序列进行排序，然后使用DFS生成所有的组合。为了避免重复，在确定当前元素的选取方案之后，应该从下一个比它大的元素所在的位置递归。
1 class Solution { 2 public: 3 vector<vector<int>> subsetsWithDup( vector<int> &S ) { 4 if( S.empty() ) { return subsets; } 5 sort( S.begin(), S.end() ); 6 vector<int> subset; 7 GenerateSub( subset, S.begin(), S.end() ); 8 return subsets; 9 } 10 private: 11 void GenerateSub( vector<int> subset, vector<int>::iterator begin, vector<int>::iterator end ) { 12 if( begin == end ) { subsets.push_back( subset ); return; } 13 auto next = upper_bound( begin, end, *begin ); 14 GenerateSub( subset, next, end ); 15 while( begin != next ) { 16 subset.push_back( *begin ); 17 GenerateSub( subset, next, end ); 18 ++begin; 19 } 20 return; 21 } 22 vector<vector<int>> subsets; 23 };
标签：des style blog color 使用 os io strong
原文地址：http://www.cnblogs.com/moderate-fish/p/3923020.html
