Practice>Python>Regex and Parsing>Validating Roman Numerals

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Validating Roman Numerals

Problem Link : https://www.hackerrank.com/challenges/validate-a-roman-number/problem

Difficulty : Easy

 

Tip

• Problem itself is simple
• We should under stand what is roman number character
• Here is regular expression, to capture roman number chracter
• (^(?=[MDCLXVI])M*(C[MD]|D?C{0,3})(X[CL]|L?X{0,3})(I[XV]|V?I{0,3})$)
• This allows MMMM, so it lead the failure of test case 4
• Please spend some time to read links below
• Best answer for this problem
• https://www.hackerrank.com/challenges/validate-a-roman-number/forum/comments/536680

 

Good explanation of Roman number character

• http://mathworld.wolfram.com/RomanNumerals.html
• https://stackoverflow.com/questions/267399/how-do-you-match-only-valid-roman-numerals-with-a-regular-expression

Solution

''' I 1 V 5 X 10 L 50 C 100 D 500 M 1000 ''' IVX = r"(?:V?I{0,3}|I[XV])" # 1, 2, ... 9 XLC = r"(?:L?X{0,3}|X[CL])" # 10, 20, ...90 CDM = r"(?:D?C{0,3}|C[MD])" # 100, 200, ... 900 M__ = r"(?:M{0,3})" # 1000, 2000, 3000 regex_pattern = rf"{M__}{CDM}{XLC}{IVX}$" import re print(str(bool(re.match(regex_pattern, input()))))