Ruby Challenge 5: Roman Numerals

gistfile1.rb

# http://www.therubygame.com/challenges/5/submissions
#  = 1
# V = 5
# X = 10
# L = 50
# C = 100
# D = 500
# M = 1000
# Sample i/o:
# MCMXCIX gives 1999, MMXII gives 2012

def to_arabic(roman)
  f = false
  o = 0
  k = { :I => 1,
        :V => 5, 
        :X => 10,
        :L => 50,
        :C => 100,
        :D => 500,
        :M => 1000}
  0.upto(roman.length - 1) do |x|
    if f; f = false;next; end
    if (roman[x+1] != nil) && (k[roman[x].to_sym] < k[roman[x+1].to_sym])
      o += (k[roman[x+1].to_sym] - k[roman[x].to_sym])
      f = true
    else
      o += k[roman[x].to_sym]
    end
  end
  o
end

puts to_arabic "XXIV"
puts to_arabic "MMXII" # 2012
puts to_arabic "XXIV" # 24