Have errors trying to test c++ solution. It occurs that RomanNumeralsHelper is already defined and the functions inside need to be renamed.

struct OtherRomanNumeralsHelper
{
   string to_roman(int value);
   int from_roman(string value);
};

string OtherRomanNumeralsHelper::to_roman(int value) {
  return "need to implement, value was: "+ to_string(value); 
} 

int OtherRomanNumeralsHelper::from_roman(string value) {
  cout << "need to implement, value was: " << value << endl;
  return 0; 
}

 OtherRomanNumeralsHelper RomanNumerals;

This let "Attempt" button to work as expected.