Trying to get better at Ruby and programming in general- here's a simple TopCoder question in Ruby

Instead of commenting on your code, I felt I had to make a rewrite. Your code is very hard to understand because of characteristics like:

• Your methods contain a lot of functionality
• Using a class without reason (e.g. no use of internal state, a lot of things being done in one class)
• Your loops are very confusing, a lot is being done in each of them

I'm aware Topcoder is a competition platform to compete in fast code, not good code, but it seems from your question you want to learn to write better Ruby code and have simply chosen a challenging situation of doing so.

This is not what I would write in a competitive environment, but may start to approach how I'd design it in a commercial application where good code is preferred is often to fast code. I've tried to break down things, so each method does as little as possible and is fairly easy to understand. Iterations upon my code would include a better way to handle the 'a-z' => 'A-Z' transition as well as figuring out a better way to do Line#ending.

require 'set'

class Poem
  attr_accessor :lines

  def initialize
    @rhymes = {"" => " "}
    @lines = []
  end

  def rhymes
    @lines.map { |line| @rhymes[line.ending] ||= next_id }
  end

  def lines=(lines)
    @lines = lines.map { |line| Line.new(line) }
  end

  private

  def next_id
    fix_last_id(@rhymes.values.last)
  end

  def fix_last_id(last)
    return 'a' if last == ' '
    return "A" if last == 'z'
    last.next
  end

  public

  class Line
    VOWELS = Set.new(['a', 'e', 'i', 'o', 'u'])

    def initialize(line)
      @line = line.downcase
      @last_word = @line.split.last || ""
    end

    def ending
      last_vowel = nil

      reverse_last_word.chars.select.each_with_index do |character, index|
        if !last_vowel || vowel_after_vowel?(last_vowel, index)
          last_vowel = index if vowel?(index)
          character
        end
      end.reverse.join
    end

    private
    def reverse_last_word
      @reverse_last_word ||= @last_word.reverse
    end

    def vowel_after_vowel?(last_vowel, index)
      (index - last_vowel == 1 && vowel?(index))
    end

    def vowel?(index)
      VOWELS.include?(reverse_last_word[index]) || y_vowel?(index)
    end

    def y_vowel?(index)
      reverse_last_word[index] == 'y' && (1...@last_word.size).include?(index)
    end
  end
end

poem = Poem.new

poem.lines = [
  "One bright day in the middle of the night",
  "Two dead boys got up to fight",
  "Back to back they faced each other",
  "Drew their swords and shot each other",
  "",
  "A deaf policeman heard the noise",
  "And came to arrest the two dead boys",
  "And if you dont believe this lie is true",
  "Ask the blind man he saw it too"
]

puts poem.rhymes.join

I haven't tried to upload it anywhere to check whether it is correct, however, it passes the public test cases.