leetcode_combination_sum

class Solution {
public:
    vector<vector<int>> combinationSum(vector<int>& candidates, int target) {
        vector<vector<int>> ret;
        vector<int> cur_vec;
        combination_sum_recur(ret,candidates,target,0,cur_vec);
        return ret;
    }
    void combination_sum_recur(vector<vector<int>> &ret, vector<int>& candidates, int target, int index, vector<int>& cur_vec)
    {
        if(target == 0)
        {
            ret.push_back(cur_vec);
        }
        else if(target > 0)
        {
            for(int i = index; i < candidates.size(); i++)
            {
                cur_vec.push_back(candidates[i]);
                combination_sum_recur(ret,candidates,target-candidates[i],i,cur_vec);
                cur_vec.pop_back();//因为程序不是并行的，所以把元素pop掉，original可以继续使用
            }
        }
        
    }
};