whiteboard.rb

#!/usr/bin/ruby

class Node
  attr_accessor :val, :left, :right

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

  def insert( val )
    if val < @val
      if @left.nil?
        @left = Node.new( val )
      else
        @left.insert( val )
      end
    elsif val > @val
      if @right.nil?
        @right = Node.new( val )
      else
        @right.insert( val )
      end
    else
      return
    end
  end

  def recursive_print
    @left.recursive_print unless @left.nil?
    print "#{@val} "
    @right.recursive_print unless @right.nil?
  end

  def nonrecursive_print
    stack = []
    node = self 
    while true
      while !node.nil?
        stack << node
        node = node.left
      end
      if !stack.empty?
        node = stack.pop
        print "#{node.val} "
        node = node.right
      else
        break
      end
    end
  end

end

puts "Input:"
node = Node.new(7)
(0..20).sort_by{ rand }.each do |val|
  print "#{val} "
  node.insert val
end

puts "\nPrinting recursively:" 
node.recursive_print

puts "\nPrinting non-recursively:"
node.nonrecursive_print

puts ""