CheckIO - Home Challenge 8 : Roman Numerals

checkio.1.08.romanNumerals.py

# CheckIO - Home Challenge 8 : Roman Numerals
# http://checkio.org

# Roman numerals come from the ancient Roman numbering system. 
# They are based on specific letters of the alphabet which are combined
# to signify the sum (or, in some cases, the difference) of their values.
# The Roman numeral system is decimal based but not directly positional and does not include a zero. 
# Roman numerals are based on combinations of these seven symbols:
# Symbol Value
#     I 1 (unus)
#     V 5 (quinque)
#     X 10 (decem)
#     L 50 (quinquaginta)
#     C 100 (centum)
#     D 500 (quingenti)
#     M 1,000 (mille)
# For this task, you should return a roman numeral using the specified integer value ranging from 1 to 3999.
# Input: A number as an integer.
# Output: The Roman numeral as a string.
# Precondition: 0 < number < 4000

ROMANS=['M','D','C','L','X','V','I']
VALUES=[1000,500,100,50,10,5,1]

def checkio(number):
    
    roman=''
    
    # Zero case
    if (number==0): return ''
    
    # Special cases
    if (str(number)[0]=='9' or str(number)[0]=='4'):
        if (number>899 and number<1000): roman+='CM'+checkio(number%100)
        if (number>399 and number<500):  roman+='CD'+checkio(number%100)
        if (number>89 and number<100): roman+='XC'+checkio(number%10)
        if (number>39 and number<50):  roman+='XL'+checkio(number%10)
        if (number==9): roman+='IX'+checkio(0)
        if (number==4): roman+='IV'+checkio(0)
        return roman
        
    # Other cases
    i=0
    while i<len(VALUES):
        value=VALUES[i]
        if number>=value:
            for x in range(0,number//value): 
                number-=value 
                roman+=ROMANS[i] + checkio(number)
                return roman
        i+=1        

if __name__ == '__main__':
    #These "asserts" using only for self-checking and not necessary for auto-testing
    assert checkio(6) == 'VI', '6'
    assert checkio(76) == 'LXXVI', '76'
    assert checkio(499) == 'CDXCIX', '499'
    assert checkio(3888) == 'MMMDCCCLXXXVIII', '3888'