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]

class Solution {

public:

    void  DFS(vector<int> &candidates, int target, int start, int sum, vector<int> &tp){

		if(sum == target){

			res.push_back(tp);

			return;

		}

		for(int i = start; i< candidates.size(); ++i){

			if(candidates[i] + sum <= target){

				tp.push_back(candidates[i]);

				DFS(candidates, target, i, sum+candidates[i], tp);

				tp.pop_back();

			}

		}

	}

    vector<vector<int> > combinationSum(vector<int> &candidates, int target) {

        // Start typing your C/C++ solution below

        // DO NOT write int main() function

        res.clear();

		int len = candidates.size();

		if(len < 1 || target <1) return res;

		sort(candidates.begin(), candidates.end());

		vector<int> tp;

		DFS(candidates, target, 0, 0, tp);

		return res;

    }

private:

	vector<vector<int>> res;

};