Linked List Sample

linked_list_sample.rb

# Joana: sample of a linked list in ruby, this was a first attempt and should (must :) be refactored!
class Node
  attr_accessor :data, :next_node

  def initialize(data, next_node = nil)
    @data = data
    @next_node = next_node
  end
end

class LinkedList
  attr_reader :size

  def initialize
    @head = nil
    @size = 0
  end

  def add(data)
    return nil unless data
    node = Node.new(data)

    if @head.nil?
      @head = node
    else
      iterator = node_at(@size - 1)
      iterator.next_node = node
    end

    @size += 1
  end

  def index(data)
    return nil unless data

    iterator = @head

    (0..@size - 1).each do |i|
      return i if iterator.data && iterator.data == data
      iterator = iterator.next_node
    end

    nil
  end

  def get(index)
    return nil unless index >= 0
    return nil unless index < @size

    iterator = @head

    (0..@size - 1).each do |i|
      return iterator.data if i == index
      iterator = iterator.next_node
    end

    nil
  end

  def remove(index)
    return nil unless index
    return nil if index < 0
    return nil if index > @size - 1

    node = node_at(index)
    previous_node = node_at(index - 1) unless index == 0

    # head
    if index == 0
      @head = node.next_node
    # tail
    elsif index == @size - 1
      previous_node.next_node = nil
    # other
    else
      previous_node.next_node = node.next_node
    end

    node.next_node = nil
    node.data = nil
    @size -= 1
  end

  private

  def node_at(index)
    iterator = @head

    (0..@size - 1).each do |i|
      return iterator if i == index
      if iterator.next_node
        iterator = iterator.next_node
      end
    end

    nil
  end

  ## More efficient way to find last node than LinkedList#node_at(index)
  # def last_node
  #   iterator = @head
  #
  #   while iterator.next_node
  #     iterator = iterator.next_node
  #   end
  #
  #   iterator
  # end
end