Ruby: Level order traversal of binary tree

level_order_traversal.rb

class BinaryTree
  attr_reader :root

  def initialize(root)
    @root = root
  end

  def level_order_traversal
    if root.nil?
      puts "Queue is empty"
      return
    end

    queue = Queue.new
    queue.enqueue(root)

    while !queue.empty? do
      node = queue.dequeue
      print "#{node.data} "

      unless node.left.nil?
        queue.enqueue(node.left)
      end

      unless node.right.nil?
        queue.enqueue(node.right)
      end
    end
  end
end

class Queue
  def initialize
    @data = []
  end

  def enqueue(element)
    @data.push(element)
  end

  def dequeue
    @data.shift
  end

  def empty?
    @data.empty?
  end
end

class TreeNode
  attr_reader :data
  attr_accessor :left, :right

  def initialize(data)
    @data = data
    @left, @right = nil, nil
  end
end

root = TreeNode.new(10)
root.left = TreeNode.new(5)
root.right = TreeNode.new(14)
root.left.left = TreeNode.new(1)
root.left.right = TreeNode.new(6)
binary_tree = BinaryTree.new(root)

puts "Level order traversal of tree :"
binary_tree.level_order_traversal
puts ""
puts ""