LeetCode 40. Combination Sum II 时间复杂度（O( n^k)）

时间复杂度（O( n^k)）,思想，DFS 深度遍历

class Solution {
public:
    vector<vector<int>> combinationSum2(vector<int>& candidates, int target) {
        vector<vector <int > >vecvec;
        if(candidates.size()==0)return vecvec;
        vector<int> vec;
        sort(candidates.begin(), candidates.end());
        combination(candidates,0,0,target,vec,vecvec);
        return vecvec;
    }
    void combination(vector<int>& candidates,int index,int sum,int target,vector<int> recVec,
                    vector<vector<int > > &vecvec){
        if(sum==target)     vecvec.push_back(recVec);
        else if(sum<target&&index<candidates.size())
            for(int k=index;k<candidates.size();++k){
                if(k>index&&candidates[k]==candidates[k-1])continue;
                if(sum+candidates[k]<=target)    {
                    recVec.push_back(candidates[k]);
                    combination(candidates,k+1,sum+candidates[k],target,recVec,vecvec);
                    recVec.pop_back();
                }
                else return ;
            }    
    }
};