roman_arabic.groovy

// http://d.hatena.ne.jp/fumokmm/20110822/1314013182
// ローマ数字定義
def romans = [
  I :1 ,
  IV:4 , V:5 , IX:9 , X:10 ,
  XL:40 , L:50 , XC:90 , C:100 ,
  CD:400, D:500, CM:900, M:1000
]

// シンボル化能力を追加
String.metaClass.getSymbol  = { delegate.intern() }
Integer.metaClass.getSymbol = { delegate.toString().intern() }
// 文字列自体に変換能力を追加
romans.each { r, a ->
  r.symbol.metaClass.toArabic = { a }
  a.symbol.metaClass.toRoman  = { r }
}

// アラビア数字 -> ローマ数字
def arabicToRoman = { int arabic ->
  ('1'*arabic).findAll(
    ~/${romans.values().sort{-it}.collect{ "1{$it}" }.join('|')}/
  )*.size()*.symbol*.toRoman().join()
}

// ローマ数字 -> アラビア数字
def romanToArabic = { String roman ->
  roman.findAll(
    ~/(${romans.keySet().sort{-it.size()}.join('|')})/
  )*.symbol*.toArabic().sum()
}

// テスト
assert arabicToRoman(11) == 'XI'
assert romanToArabic('XI') == 11
assert arabicToRoman(12) == 'XII'
assert romanToArabic('XII') == 12
assert arabicToRoman(14) == 'XIV'
assert romanToArabic('XIV') == 14
assert arabicToRoman(18) == 'XVIII'
assert romanToArabic('XVIII') == 18
assert arabicToRoman(24) == 'XXIV'
assert romanToArabic('XXIV') == 24
assert arabicToRoman(43) == 'XLIII'
assert romanToArabic('XLIII') == 43
assert arabicToRoman(99) == 'XCIX'
assert romanToArabic('XCIX') == 99
assert arabicToRoman(495) == 'CDXCV'
assert romanToArabic('CDXCV') == 495
assert arabicToRoman(1888) == 'MDCCCLXXXVIII'
assert romanToArabic('MDCCCLXXXVIII') == 1888
assert arabicToRoman(1945) == 'MCMXLV'
assert romanToArabic('MCMXLV') == 1945
assert arabicToRoman(3999) == 'MMMCMXCIX'
assert romanToArabic('MMMCMXCIX') == 3999

roman_arabic.py

import re

def getArabicRomanTable():
  t = {
    1: 'I',
    5: 'V',
    10: 'X',
    50: 'L',
    100: 'C',
    500: 'D',
    1000: 'M',
  }
  for k in [x for x in t.keys() if x > 1]:
    if str(k)[0] == '1':
      t[9*k/10] = t[k/10] + t[k]
    else:
      t[8*k/10] = t[k/5] + t[k]
  return t

def arabicToRoman(n):
  if not (isinstance(n, int) and 0 < n < 4000):
    raise
  t = getArabicRomanTable()
  r = ''
  for k in sorted(t.keys(), reverse=True):
    r += t[k] * (n / k)
    n = n % k
  return r

def romanToArabic(s):
  if not (isinstance(s, str) and re.compile('^[IVXLCDMivxlcdm]+$').match(s)):
    raise
  s = s.upper()
  t = {}
  r = 0
  for k, v in getArabicRomanTable().items():
    t[v] = k
  for k in [x for x in t.keys() if len(x) > 1]:
    r += t[k] * s.count(k)
    s = s.replace(k, '')
  for k in [x for x in t.keys() if len(x) == 1]:
    r += t[k] * s.count(k)
  return r

if __name__ == '__main__':
  assert arabicToRoman(11) == 'XI'
  assert arabicToRoman(12) == 'XII'
  assert arabicToRoman(14) == 'XIV'
  assert arabicToRoman(18) == 'XVIII'
  assert arabicToRoman(24) == 'XXIV'
  assert arabicToRoman(43) == 'XLIII'
  assert arabicToRoman(99) == 'XCIX'
  assert arabicToRoman(495) == 'CDXCV'
  assert arabicToRoman(1888) == 'MDCCCLXXXVIII'
  assert arabicToRoman(1945) == 'MCMXLV'
  assert arabicToRoman(3999) == 'MMMCMXCIX'
  assert romanToArabic('XI') == 11
  assert romanToArabic('XII') == 12
  assert romanToArabic('XIV') == 14
  assert romanToArabic('XVIII') == 18
  assert romanToArabic('XXIV') == 24
  assert romanToArabic('XLIII') == 43
  assert romanToArabic('XCIX') == 99
  assert romanToArabic('CDXCV') == 495
  assert romanToArabic('MDCCCLXXXVIII') == 1888
  assert romanToArabic('MCMXLV') == 1945
  assert romanToArabic('MMMCMXCIX') == 3999