DoubleLinkedListRuby

gistfile1.rb

class Node
  attr_accessor :prev_node, :next_node

  def initialize(data)
    @data = data
  end

  def has_next?()
    @next_node ? true : false
  end

  def has_prev?()
    @prev_node ? true : false
  end

  def data
    return @data
  end

  def print()
    puts @data.to_s
  end
end

class DoublyLinkedList

  def initialize(node)
    @root_node = node
  end

  def last
    pointer = @root_node
    pointer = pointer.next_node while pointer.has_next?
    pointer
  end

  def insert_tail(node)
    last.next_node = node
    node.prev_node = last
  end

  def first
    pointer = @root_node
    while pointer.has_prev?
      pointer = pointer.prev_node
    end
    pointer
  end

  def insert_head(node)
    node.next_node = first
    node.prev_node = nil
    @root_node = node
  end

  def delete(value)
    pointer = @root_node
    if pointer.data == value
      @root_node = @root_node.next_node
      @root_node.prev_node = nil
      pointer = nil
    else
      while pointer.has_next?
        pointer = pointer.next_node
        if pointer.data == value
          pointer.prev_node.next_node = pointer.next_node
          pointer.next_node.prev_node = pointer.prev_node
          return
        end
      end
    end
  end

  def print()
    pointer = @root_node
    while pointer != nil
      pointer.print
      pointer = pointer.next_node
    end
  end
end