roman-numerals

Created by @theoludwig on 30 June 2021.

Instructions

The objective of this challenge is to create a function that translates a number into Roman numerals or the other way around.

We will use the letters I, V, X, L, C, D, M to build the Roman numerals.

Here are the rules for building a Roman numeral:

The numbers 1, 2 and 3 are written respectively as I, II and III
The number 5 is written as V
The number 10 is written as X
The number 50 is written as L
The number 100 is written as C
The number 500 is written as D
The number 1000 is written as M
When writing two letters in a row, if the numerical value of the first is greater than the numerical value of the second, their numerical values are added. For example the number 6 is written VI. We add V (5) + I (1) = 6.
When writing two letters in a row, if the numerical value of the first is less than the numerical value of the second, the value of the first is subtracted from the second. For example the number 4 is written IV. We subtract V (5) - I (1) = 4.
Subtractions of values are limited to 2 letters only. For example we cannot write 8 while doing IIX. We must use the addition of letters like this VIII.
Therefore, the first ten numbers are written as I, II, III, IV, V, VI, VII, VIII, IX, X . Larger numbers follow the same pattern.
You can associate as many symbols as you want to write larger numbers, for example:
- 36 is written as XXXVI
- 42 is written as XLII
- 2448 is written as MMCDXLVIII.

Symbol	I	V	X	L	C	D	M
Value	1	5	10	50	100	500	1000

Line 1: The string : arabic to roman or roman to arabic to determine how to convert the number
Line 2: The number to convert

See the test folder for examples of input/output.