gistfile1.rb

class LinkedList
  include Enumerable

  attr_reader :head

  class Node
    attr_reader :value
    attr_accessor :next

    def initialize(value, _next = nil)
      @value = value
      @next = _next
    end

    def inspect
      value.inspect
    end
  end

  def initialize(ary = nil)
    @head = Node.new(nil) # head element
    @last = @head
    if ary
      ary.each {|value| add(value)}
    end
    self
  end

  def insert_after(where, value)
    value = Node.new(value, where.next)
    where.next = value
    @last = value if where == @last
    value
  end

  def each
    p = @head.next
    while p
      yield p.value
      p = p.next
    end

    self
  end

  def add(value)
    insert_after(@last, value)
  end

  def inspect
    to_a.inspect
  end
end