Romans

roman.rb

# Roman numbers values
ROMAN_VALUES = {
  1000 => "M",
   900 => "CM",
   500 => "D",
   400 => "CD",
   100 => "C",
    90 => "XC",
    50 => "L",
    40 => "XL",
    10 => "X",
     9 => "IX",
     5 => "V",
     4 => "IV",
     1 => "I"
}


def roman_to_integer(str = self, result = 0)
  # return 0 if string is empty
  return result if str.empty?

  # check if string start with a roman value
  ROMAN_VALUES.values.each do |roman|
    if str.start_with?(roman)                   # start with roman value
      result += ROMAN_VALUES.invert[roman]      # add value to result
      str = str.slice(roman.length, str.length) # delete roman processed from string
      return roman_to_integer(str, result)      # recursive call to process the rest of string
    end
  end
end

# Read file
text = File.open("#{ARGV[0]}").read.split

# for each line convert roman to integer
text.each do |roman|
  puts "#{roman} => #{roman_to_integer(roman)}"
end