integer_to_roman.rb

MAP = {
  1 => ['I', 'V', 'X'],
  2 => ['X', 'L', 'C'],
  3 => ['C', 'D', 'M'],
  4 => ['M', 'M', 'M']
}

def to_roman(numeral)
  roman_numeral = ''

  i = 1

  loop do
    place = numeral % 10
    this_place = ''

    if i == 4
      this_place = MAP[i][0] * place
      roman_numeral = this_place + roman_numeral
      break
    elsif place.between?(1,3)
      this_place = MAP[i][0] * place
    elsif place == 4
      this_place = MAP[i][0] + MAP[i][1]
    elsif place.between?(5,8)
      this_place = MAP[i][1]
      this_place += MAP[i][0] * (place - 5)
    elsif place == 9
      this_place = MAP[i][0] + MAP[i][2]
    elsif place == 0 && i == 3
      i += 1 
    end

    roman_numeral = this_place + roman_numeral

    i += 1 if i < 4
    numeral /= 10
    break if numeral == 0
  end

  roman_numeral
end