Ruby tree with BF and DF traversal

tree.rb

# extended from https://stackoverflow.com/questions/10661610/implement-a-tree-iterator 

class Node
  attr_accessor :data, :children

  def initialize(data, *children)
    @data = data
    @children = children
  end

  def traverse_depth(&block)
    yield self
    children.each {|child| child.traverse_depth(&block)}
  end

  def traverse_breadth(&block)
    queue = [self]
    while !queue.empty?
      node = queue.shift
      yield node
      queue += node.children
    end
  end
end

z = Node.new("d", Node.new("0"))
b = Node.new("b", z)
c = Node.new("c", Node.new("e"))
root = Node.new("A", b, c)

str = ''
root.traverse_depth {|node| str += node.data}
print str

puts
str = ''
root.traverse_breadth {|node| str += node.data}
print str

Alternatively, node, *queue = queue in-place of node = queue.shift