Leetcode: Combination Sum

Given a set of candidate numbers (C) 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.
Elements in a combination (a1, a2, … , ak) must be in non-descending order. (ie, a1 ≤ a2 ≤ … ≤ ak).
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] 

void comb(vector<int> candidates, int index, int sum, int target, vector<vector<int>> &res, vector<int> &path)
    {
    	if(sum>target)return;
		if(sum==target){res.push_back(path);return;}
		for(int i= index; i<candidates.size();i++)
		{
			path.push_back(candidates[i]);
			comb(candidates,i,sum+candidates[i],target,res,path);
			path.pop_back();
		}
	}
	vector<vector<int> > combinationSum(vector<int> &candidates, int target) {
        // Note: The Solution object is instantiated only once.
        sort(candidates.begin(),candidates.end());
		vector<vector<int>> res;
		vector<int> path;
		comb(candidates,0,0,target,res,path);
		return res;
    }