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();
           }
       }
    }

};