Calculate A Maximum Value Recursively

max.cc

#include <iostream>
#include <stdexcept>

int max(int numbers[], unsigned int len)
{
  std::cout << "len=" << len << ": starting function." << std::endl;

  if (len == 0)
  {
    throw std::invalid_argument("len must not be zero");
  }
  else if (len == 1)
  {
    std::cout << "len=" << len << ": base case returning " << numbers[0] << std::endl;
    return numbers[0];
  }
  else
  {
    std::cout << "len=" << len << ": about to launch recursive call with len=" << len - 1 << std::endl;
    int maxOfRest = max(numbers, len - 1);
    std::cout << "len=" << len << ": recursive call complete." << std::endl;

    int finalNumber = numbers[len - 1];

    std::cout << "len=" << len << ": comparing maxOfRest=" << maxOfRest << " and finalNumber=" << finalNumber << std::endl;
    if (maxOfRest > finalNumber)
    {
      std::cout << "len=" << len
                << ": complete, returning " << maxOfRest << std::endl;
      return maxOfRest;
    }
    else
    {
      std::cout << "len=" << len
                << ": complete, returning " << finalNumber << std::endl;
      return finalNumber;
    }
  }
}

int main()
{
  int numbers[5] = {19, 53, 31, 43, 24};

  int maxValue = max(numbers, 5);

  std::cout << "the max is: " << maxValue << std::endl;

  return 0;
}