39. Combination Sum LeetCode

std::vector<std::vector<int>> combinationSum(std::vector<int> &candidates, int target)
{
   std::vector<std::vector<int>> combinations;
   std::vector<int> currentCombination;
   backtrack(candidates, combinations, currentCombination, 0, target);
   return combinations;
}

void backtrack(std::vector<int> &candidates, std::vector<std::vector<int>> &combinations,
               std::vector<int> &currentCombination,
               int idx, int currentValue)
{
   if (currentValue < 0)
      return;

   else if (currentValue == 0)
   {
      combinations.push_back(currentCombination);
      return;
   }

   for (int i = idx; i < candidates.size(); ++i)
   {
      currentCombination.push_back(candidates[i]);
      backtrack(candidates, combinations, currentCombination, i, currentValue - candidates[i]);
      currentCombination.pop_back();
   }
}