Create 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]