Combination Sum

Given a set of candidate numbers (C) (without duplicates) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.

The same repeated number may be chosen from C unlimited number of times.

Note:
All numbers (including target) will be positive integers.
The solution set must not contain duplicate combinations.
For example, given candidate set [2, 3, 6, 7] and target 7,
A solution set is:
[
[7],
[2, 2, 3]
]

方法:DFS

class Solution {
private:
    void find(vector<vector<int>>& res,vector<int>& candidates,vector<int>& buffer, const int& target, int index,int temp_sum){
        if(temp_sum > target){
            return;
        }
        else if(temp_sum == target){
            res.push_back(buffer);
            return ;
        }

        for(int i = index ; i < candidates.size() ; ++i){
            buffer.push_back(candidates[i]);
            find(res,candidates,buffer,target,i,temp_sum+candidates[i]);
            buffer.pop_back();
        }

    }

public:
    vector<vector<int>> combinationSum(vector<int>& candidates, int target) {
        vector<vector<int>> res;
        vector<int> buffer;
        find(res,candidates,buffer,target,0,0);
        return res;



    }
};