never do this

horrible_v1.cpp

#include <iostream>
#include <fstream>
#include <algorithm>
#include <string>
#include <vector>
#include <sstream>

void foo(const char* filepath)
{
  std::ifstream file(filepath);
  if (!file.is_open())
  {
    std::cerr << "Failed to open: " << filepath << '\n';
  }

  std::string line;
  std::getline(file, line);
  size_t colcount = std::count(std::begin(line), std::end(line), ',') + 1;

  std::vector<int> sums(colcount);

  size_t rowcount{};
  for (; std::getline(file, line, '\n'); ++rowcount)
  {
    std::stringstream stream;
    stream << line;
    std::string num;
    for(size_t i{}; i < colcount; ++i)
    {
      std::getline(stream, num, ',');
      sums[i] += std::stoi(num);
    }
  }

  size_t mean = 2;
  size_t sum = 3;

  std::cout << "1[MEAN]: " << (static_cast<double>(sums[mean - 1]) / rowcount) << '\n';
  std::cout << "2[SUM]: " << sums[sum - 1] << '\n';
}

int main()
{
  constexpr auto filepath =
   "/home/dev/projects/_cpp/_challenge/clean-code-competition17/task1/test.small";

  foo(filepath);

  return 0;
}