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] 

 

DFS!

1 class Solution { 2 public: 3     void findNext(vector
     
      
        > &res, vector
       
         &candidates, vector
        
          v, int sum, int target, int idx) { 4         if (sum > target || idx >= candidates.size()) { 5             return; 6         } 7         if (sum == target) { 8             res.push_back(v); 9             return;10         }11         v.push_back(candidates[idx]);12         findNext(res, candidates, v, sum + candidates[idx], target, idx);13         v.pop_back();14         findNext(res, candidates, v, sum, target, idx + 1);15     }16     17     vector
         
          
            > combinationSum(vector
           
             &candidates, int target) {18 vector
            
             
               > res;19 sort(candidates.begin(), candidates.end());20 vector
              
                v;21 findNext(res, candidates, v, 0, target, 0);22 return res;23 }24 };