Roman Numerals Kata

This is a Roman Numerals Kata with RSpec tests. Specs fail fast on first error and run in order to give a step by step flow.

Try to come up with elegant solutions without breaking or changing any spec.

Run tests with guard

For speed and comfort we can run the specs with bundle exec guard which will run them on every file change.

Example Algorithm

Roman to Arabic:

Given a roman number like XI, iterate through each letter and add it's numeric value to a variable.

Example:

Input = XI

X = 10 I = 1

Result = 10 + 1 = 11

Special Cases:

• When the next letter numerical value is bigger than itself instead of adding, we need to subtract.

Eg: IX

I = 1 X = 10

Result = -1 + 10 = 9

Arabic to Roman

Giving a number, keep reducing it to roman figures and add them to a string variable until the number is zero.

Example:

result = ''

number = 17 . It's less than 40 (XL) and bigger than 10 (X) so lets subtract 10.

number -= 10 result << X

number = 7 It's less than 9 (IX) and bigger than 5 (V) so lets subtract 5.

number -= 5 result << V

number = 2 It's less than 4 (IV) and bigger than 1 (I) so lets subtract 1.

number -= 1 result << I

number -= 1 result << I

result is now: XVII