notate rational number including cyclical one. e.g. to_rational(1, 7) == "0.(142857)"

to_rational.cpp

std::string to_rational(int numerator, int denominator)
{
  std::string result;
  int n = numerator / denominator;
  result += std::to_string(n);

  if (numerator % denominator == 0) return result;

  result += ".";

  int remainder = numerator % denominator;
  std::vector<int> place, rems;
  std::vector<int>::iterator it;

  while ((it = std::find(rems.begin(), rems.end(), remainder)) == rems.end())
  {
    rems.push_back(remainder);
    place.push_back(remainder * 10 / denominator);
    remainder = remainder * 10 % denominator;
    if (remainder == 0)
    {
      for (int p : place) result.push_back(p + '0');
      return result;
    }
  }

  int idx = std::distance(rems.begin(), it);
  for (int i = 0; i < place.size(); ++i)
  {
    if (i == idx) result += "(";
    result += place[i] + '0';
  }
  result += ")";

  return result;
}