pointers-tests.rb

require 'rubygems'
require 'test/unit'
require 'shoulda'

require 'pointers'

class ListNodeTest < Test::Unit::TestCase
  context "A LinkedList instance" do
    setup do
      @list = LinkedList.new
      @list.insert!('Not Boomshakalaka')
      @list.insert!('still not it')
      @list.insert!('definitely not')
    end

    context "containing Boomshakalaka" do
      setup do
        @list.insert!('Boomshakalaka')
      end

      should "contain Boomshakalaka" do
        assert_equal true, @list.contains?('Boomshakalaka')
      end
    end

    context "containing Boomshakalaka a few elements down" do
      setup do
        @list.insert!('Boomshakalaka')
        @list.insert!('Always')
        @list.insert!('Be')
        @list.insert!('Coding')
      end

      should "contain Boomshakalaka" do
        assert_equal true, @list.contains?('Boomshakalaka')
      end
    end

    context "not containing Boomshakalaka" do
      setup do
        @list.insert!('dusty room')
        @list.insert!('tumbleweed')
      end

      should "not contain Boomshakalaka" do
        assert_equal false, @list.contains?('Boomshakalaka')
      end
    end
  end
end

pointers.rb

class ListNode < Object
  attr_accessor :data, :next, :prev
end

class LinkedList

  # Insert an item into the front of the list
  def insert!(item)
    node = ListNode.new
    node.data = item
    node.prev = nil
    node.next = @head

    @head.prev = node unless @head.nil?

    @head = node
  end

  # Find given item in list
  def contains?(item)
    node = @head
    while node
      return true if node.data == item
      node = node.next
    end
    return false
  end

  # Traverse list
  def inspect
    node = @head
    trav = ""
    while node
      trav += " <- #{node.data} -> "
      node = node.next
    end

    return trav
  end

end