1. 题目

Combination Sum II

2. 算法

http://www.cnblogs.com/grandyang/p/4419386.html

• DFS:O(n!)

3. 代码

class Solution{

public:

    vector<vector<int> > combinationSum(vector<int>& candidates,int target){

        vector<vector<int> > res;

        vector<int> out;

        sort(candidates.begin(),candidates.end());

        combinationDFS(candidates,target,0,out,res);

        return res;

    }

private:

    void combinationDFS(vector<int>& candidates,int target,int start,vector<int>& out,vector<vector<int> >& res){

       if(target<0)  return ;

        else if(target==0)  res.push_back(out);

        else{

           for(int i=start;i<candidates.size();++i){

               if(i>start && candidates[i]==candidates[i-1]) continue;

               out.push_back(candidates[i]);

               combinationDFS(candidates,target-candidates[i],i+1,out,res);

               out.pop_back();

           }

       }

    }

};