[RUBY] Let's solve the roman numerals

https://qiita.com/knkrhs/items/27440e1c7f75cc5f53f0

Challenges Write a method that takes arabic numerals and returns roman numerals

Cheeks, it's pretty interesting. So, let's solve this. It's New Year's Eve, and sometimes it's good!

digittoarabic.rb

DigitToRoman = Struct.new(:arabic, :roman )

def roman(n)
    #Supports from 1 to 3999
    if n <= 0 || n >= 4000 then
        raise "Invalid input(" + n.to_s + ")"
    end

    #Create a table for conversion.
    #Actually, it is better to use initilize timing in Class.
    v = Array.new()
    v.push ( DigitToRoman.new( 1000, "M") )
    v.push ( DigitToRoman.new(  900, "CM") )
    v.push ( DigitToRoman.new(  500, "D") )
    v.push ( DigitToRoman.new(  400, "CD") )
    v.push ( DigitToRoman.new(  100, "C") )
    v.push ( DigitToRoman.new(   90, "XC") )
    v.push ( DigitToRoman.new(   50, "L") )
    v.push ( DigitToRoman.new(   40, "XL") )
    v.push ( DigitToRoman.new(   10, "X") )
    v.push ( DigitToRoman.new(    9, "IX") )
    v.push ( DigitToRoman.new(    5, "V") )
    v.push ( DigitToRoman.new(    4, "IV") )
    v.push ( DigitToRoman.new(    1, "I") )

    #Reverse sort
    #You can sort and then reverse, but the cost is ...
    #If you don't sort, the result will change if the push order above changes.
    v = v.sort{|a,b| -( a.arabic <=> b.arabic ) }

    #Conversion to Roman numeral strings.
    #Eliminate loops in the conversion table by using inject
    #Also, a character string*Make a string with numbers and repeat
    v.inject("") { |ret, m|
        i = n / m.arabic
        n = n % m.arabic
        ret + m.roman * i
    }
end

num = ARGV[0].to_i
puts ARGV[0] + " = " + roman(num)

!ruby 2.7.1p83