RomanToArabic.groovy

class RomanConverter {
    final static def VALUES = [
        'I': 1,
        'V': 5,
        'X': 10,
        'L': 50,
        'C': 100,
        'D': 500,
        'M': 1000
    ];
    
    final static def romanToArabic(String roman = "") {
        if (roman == null || roman.isEmpty()) {
            return null;
        }
        
        def number = roman.toUpperCase()

        if (! number.every { d -> VALUES.any { k, v -> d == k }}) {
            return null;
        }

        if(number.length() == 1) return VALUES.get(number[0], null)
        
        def n1, n2
        def total = 0
        def c = 0
        
        while (c < number.length()) {
            n1 = VALUES.getAt(number[c])
            
            if (c+1 < number.length()) {
                n2 = VALUES.getAt(number[c+1])
                if (n1 >= n2) {
                    total += n1
                    c += 1
                } else {
                    total += n2 - n1
                    c += 2
                }
            }
            else {
                total += n1
                c += 1
            }
        }
        return total
    }
    
    final static def arabicToRoman(String number) { }
}

assert RomanConverter.romanToArabic(null) == null
assert RomanConverter.romanToArabic("") == null
assert RomanConverter.romanToArabic("invalid") == null
assert RomanConverter.romanToArabic("I") == 1
assert RomanConverter.romanToArabic("IV") == 4
assert RomanConverter.romanToArabic("VI") == 6
assert RomanConverter.romanToArabic("IX") == 9
assert RomanConverter.romanToArabic("ix") == 9
assert RomanConverter.romanToArabic("X") == 10

assert RomanConverter.romanToArabic("MCMXC") == 1990
assert RomanConverter.romanToArabic("MCMXCI") == 1991
assert RomanConverter.romanToArabic("MCMXCII") == 1992
assert RomanConverter.romanToArabic("MCMXCIII") == 1993
assert RomanConverter.romanToArabic("MCMXCIV") == 1994
assert RomanConverter.romanToArabic("MCMXCV") == 1995
assert RomanConverter.romanToArabic("MCMXCVI") == 1996
assert RomanConverter.romanToArabic("MCMXCVII") == 1997
assert RomanConverter.romanToArabic("MCMXCVIII") == 1998
assert RomanConverter.romanToArabic("MCMXCIX") == 1999

assert RomanConverter.romanToArabic("MM") == 2000
assert RomanConverter.romanToArabic("MMI") == 2001
assert RomanConverter.romanToArabic("MMII") == 2002
assert RomanConverter.romanToArabic("MMIII") == 2003
assert RomanConverter.romanToArabic("MMIV") == 2004
assert RomanConverter.romanToArabic("MMV") == 2005
assert RomanConverter.romanToArabic("MMVI") == 2006
assert RomanConverter.romanToArabic("MMVII") == 2007
assert RomanConverter.romanToArabic("MMVIII") == 2008
assert RomanConverter.romanToArabic("MMIX") == 2009
assert RomanConverter.romanToArabic("MMX") == 2010

assert RomanConverter.romanToArabic("MMMM") == 4000
assert RomanConverter.romanToArabic("MMMMCMXCIX") == 4999

println("End")