Create a binary tree from an array in ruby

binary_tree.rb

# Ruby program to create binary tree from array of numbers
# Class Node to store value, left node and right node
class Node
  attr_accessor :value, :left, :right

  def initialize(value = nil)
    self.value = value
  end
end

# Tree class
class BinaryTree
  attr_accessor :root

  def initialize
    self.root = Node.new
  end

  # Abstracted method to create and
  # @param [Array] array: numbers array eg. [1, 2, 3, 4, 5, 6, 6, 6, 6]
  def self.create_binary_tree(array)
    tree = BinaryTree.new
    tree.root = insert_level_order(array, tree.root, 0)
    print "In-order traversal: "
    tree.in_order_traversal(tree.root)
    print "\nPre-order traversal: "
    tree.pre_order_traversal(tree.root)
    print "\nPost-order traversal: "
    tree.post_order_traversal(tree.root)
  end

  # Function to insert nodes in level order
  def self.insert_level_order(array, node, index)
    return node if index > array.size
    temp = Node.new(array[index])
    root = temp
    root.left = insert_level_order(array, root.left, index * 2 + 1)
    root.right = insert_level_order(array, root.right, index * 2 + 2)
    root
  end

  # This method does in-order traversal and print the tree
  def in_order_traversal(root)
    return if root.nil?
    in_order_traversal(root.left)
    print root.value.to_s + ' '
    in_order_traversal(root.right)
  end
  
  # This method does pre-order traversal and print the tree
  def pre_order_traversal(root)
    return if root.nil?
    print root.value.to_s + ' '
    pre_order_traversal(root.left)
    pre_order_traversal(root.right)
  end
  
  # This method does post-order traversal and print the tree
  def post_order_traversal(root)
    return if root.nil?
    post_order_traversal(root.left)
    post_order_traversal(root.right)
    print root.value.to_s + ' '
  end
end

# calling method to create and print binary tree.
BinaryTree.create_binary_tree([1, 2, 3, 4, 5, 6, 6, 6, 6])