Solution 9: Integer to Roman Numeral

Given an integer between 1 and 3999, convert it to a Roman numeral. Return a string of the Roman numeral representation.

def int_to_roman(num)
  remainder = num
  numeral = ''
  while remainder > 0
    (string, remainder) = get_string_remainder(numeral, remainder)
    numeral += string
  end
  numeral
end

def get_string_remainder(str, int)
  return '' if int === 0
  if int.to_s[0] == '9'
    if int > 899
      int = int - 900
      string = 'CM'
    elsif int > 89
      int = int - 90
      string = 'XC'
    elsif int > 8
      int = int - 9
      string = 'IX'
    end
  elsif int.to_s[0] == '4'
    if int > 399
      int = int - 400
      string = 'CD'
    elsif int > 39
      int = int - 40
      string = 'XL'
    elsif int > 3
      int = int - 4
      string = 'IV'
    end
  elsif (int - 1000 >= 0)
    int = int - 1000
    string = 'M'
  elsif (int - 500 >= 0)
    int = int - 500
    string = 'D'
  elsif (int - 100 >= 0)
    int = int - 100
    string = 'C'
  elsif (int - 50 >= 0)
    int = int - 50
    string = 'L'
  elsif (int - 10 >= 0)
    int = int - 10
    string = 'X'
  elsif (int - 5 >= 0)
    int = int - 5
    string = 'V'
  else
    int = int - 1
    string = 'I'
  end

  [string, int]
end