Roman Numerals Parser

def parse_roman(roman)
  roman_numerals = [ ['M', 1000], ['CM', 900], ['D', 500], ['CD', 400], ['C', 100], ['XC', 90],
            ['L', 50], ['XL', 40], ['X', 10], ['IX', 9], ['V', 5], ['IV', 4], ['I', 1] ]
  roman = roman.upcase
  result = 0
  roman_numerals.each do |sym, val|
    while roman.sub!(/^#{sym}/, "")
      result += val
    end
  end
  result
end

# "CM" = 900, which we get by "M" (1000) + "C" (100) + "CM" (-200)
# much easier code than otherwise
def parse_roman_2(roman)
  roman_numerals = [
            ['M', 1000], ['CM', -200],
            ['D', 500], ['CD', -200],
            ['C', 100], ['XC', -20],
            ['L', 50], ['XL', -20],
            ['X', 10], ['IX', -2],
            ['V', 5], ['IV', -2],
            ['I', 1]
  ]
  roman = roman.upcase
  roman_numerals.map{|sym, val| val * roman.scan(sym).size}.inject(0, &:+)
end

["MCMXC", "MMVIII", "MDCLXVI"].each {|r| puts "%8s :%5d  :%5d " % [r, parse_roman(r), parse_roman_2(r)]}