Roman numerals

Create a method that takes Arabic numerals as input and returns Roman numerals.

Answer (before refactoring)

It's wasteful and it's a level that shouldn't be seen for a long time, so I fold it.

def getNums()
  lines = readlines
  len = lines.length

  (0..len-1).each do |i|
    lines[i] = lines[i].chomp.to_i
  end

  return lines
end

class Integer
  def to_roman
    sym = ['I', 'V', 'X', 'L', 'C', 'D', 'M']
    roman = ''
    to_arr(4).each_with_index do |num, i|
      case i
      when 0 then
	roman += sym[6] * num
      when 1 then
	case num
	when 0..3 then
	  roman += sym[4] * num
	when 4 then
	  roman += sym[4] + sym[5]
	when 5..8 then
	  roman += sym[5] + sym[4] * (num-5)
	when 9 then
	  roman += sym[4] + sym[6]
	end
      when 2 then
	case num
	when 0..3 then
	  roman += sym[2] * num
	when 4 then
	  roman += sym[2] + sym[3]
	when 5..8 then
	  roman += sym[3] + sym[2] * (num-5)
	when 9 then
	  roman += sym[2] + sym[4]
	end
      when 3 then
	case num
	when 0..3 then
	  roman += sym[0] * num
	when 4 then
	  roman += sym[0] + sym[1]
	when 5..8 then
	  roman += sym[1] + sym[0] * (num-5)
	when 9 then
	  roman += sym[0] + sym[2]
	end
      end
    end
    roman
  end

  def to_arr(n)
    arr = []
    (Math.log10(self).to_i + 1).upto(n-1) do
      arr.unshift(0)
    end
    arr + digits.reverse
  end
end

if $PROGRAM_NAME == __FILE__
  getNums().each do |i|
    puts i.to_roman
  end
end

Answer (after refactoring)

def getNums()
  lines = readlines

  (0..lines.length-1).each do |i|
    lines[i] = lines[i].chomp.to_i
  end
  lines
end

class Integer
  def to_roman
    sym = ['I', 'V', 'X', 'L', 'C', 'D', 'M']
    roman = ''
    base = sym.length-1
    to_arr(4).each_with_index do |num, i|
      case num
      when 0..3 then
	roman += sym[base-i*2] * num
      when 4 then
	roman += sym[base-i*2] + sym[base-i*2+1]
      when 5..8 then
	roman += sym[base-i*2+1] + sym[base-i*2] * (num-5)
      when 9 then
	roman += sym[base-i*2] + sym[base-(i-1)*2]
      end
    end
    roman
  end

  def to_arr(n)
    arr = Array.new(n - Math.log10(self).to_i - 1, 0)
    arr + digits.reverse
  end
end

if $PROGRAM_NAME == __FILE__
  getNums().each do |i|
    # puts "#{i} => #{i.to_roman}"
    printf("%4d => %s\n", i, i.to_roman)
  end
end

Commentary

Receive input of Arabic numerals

def getNums()
  lines = readlines

  (0..lines.length-1).each do |i|
    lines[i] = lines[i].chomp.to_i
  end
  lines
end

This is the part that receives input from standard input.

--Since it is intended for multi-line input, you can enter it separated by line breaks. --Cast the string with the line feed code removed to Integer and store it as an array in lines.

Execution part

if $PROGRAM_NAME == __FILE__
  getNums().each do |i|
    # puts "#{i} => #{i.to_roman}"
    printf("%4d => %s\n", i, i.to_roman)
  end
end

This is the part that is executed when the program is executed with $ ruby roman_numerals.rb etc.

--Receive the input with getNums () and output it to the return object (array) as standard output. --As will be described later, since it is overridden to the Integer class, you can get Roman numerals as a character string with (Integer) .to_roman.

Method to return Roman numerals

class Integer
  def to_roman
    sym = ['I', 'V', 'X', 'L', 'C', 'D', 'M']
    roman = ''
    base = sym.length-1
    to_arr(4).each_with_index do |num, i|
      case num
      when 0..3 then
	roman += sym[base-i*2] * num
      when 4 then
	roman += sym[base-i*2] + sym[base-i*2+1]
      when 5..8 then
	roman += sym[base-i*2+1] + sym[base-i*2] * (num-5)
      when 9 then
	roman += sym[base-i*2] + sym[base-(i-1)*2]
      end
    end
    roman
  end

  def to_arr(n)
    arr = Array.new(n - Math.log10(self).to_i - 1, 0)
    arr + digits.reverse
  end
end

This is the implementation part of this time.

--Implemented to override the Integer class.

To an array of 4 elements (to \ _arr (n))

--Roman numerals can represent 1 to 3999. - to_arr(n) --This method arranges the entered Arabic numerals by dividing them into digits. -- n means the maximum number of digits, and numbers less than that digit are padded with zeros. --Example

n = 8
n.to_arr(4) # [0, 0, 0, 8]

To Roman numerals

--Refer to Wikipedia etc. for each symbol of Roman numerals. --The Roman numerals to be assembled are stored in the string variable roman. - to_arr(4).each_with_index -- self can be omitted, so it is omitted. --Convert to a 4-element array with to_arr (4), and then process each digit. --Cases are classified according to the case statement. The most important Roman numerals are 4 and 9. --The processing for each number is the concept and array of Roman numerals in Wikipedia above sym = ['I','V','X','L','C','D','M' You can understand it by comparing with] . --The final Roman numeral roman is output. --Example

n = 8
n.to_roman # "VIII"
n = 1999
n.to_roman # "MCMXCIX"

Execution result

First, prepare the following text file (in.txt) as input.

The execution result when this is given as input is as follows.

$ ruby roman_numerals.rb < in.text
   1 => I
   2 => II
   4 => IV
   5 => V
   6 => VI
   9 => IX
  10 => X
  11 => XI
  14 => XIV
  15 => XV
  19 => XIX
  38 => XXXVIII
  42 => XLII
  49 => XLIX
  51 => LI
  97 => XCVII
  99 => XCIX
 439 => CDXXXIX
 483 => CDLXXXIII
 499 => CDXCIX
 732 => DCCXXXII
 961 => CMLXI
 999 => CMXCIX
1999 => MCMXCIX

moved!!!!!

source ~/Library/Mobile Documents/com~apple~CloudDocs/KG/class/M1/multi_scale_sim/grad_members_20f/members/ryomichi56/./qiita/roman_numerals.org

Find Roman numerals in Ruby