Getting started with Binary Trees and Ruby

my_tree.rb

# Example:
#
#     1
#    / \
#   2  12
#  /
# 4

class Node
  attr_accessor :left, :right, :value

  def initialize(left, right, value)
    @left = left
    @right = right
    @value = value
  end
end

class Tree
  def initialize
    left = Node.new(nil,nil,2)
    right = Node.new(nil,nil,12)
    left.left = Node.new(nil,nil,4)
    @root = Node.new(left, right, 1)
  end

  def depth
    puts tree_depth(@root)
  end

  def values
    tree_values(@root); puts
  end

  def max
    puts tree_max(@root)
  end

  def min
    puts tree_min(@root)
  end

  def total
    puts tree_total(@root)
  end

private
  def tree_values(node)
    print("#{node.value} ")
    tree_values(node.left) unless node.left.nil?
    tree_values(node.right) unless node.right.nil?
  end

  def tree_depth(node)
    return 0 if node.nil?
    left = tree_depth(node.left) + 1
    right = tree_depth(node.right) + 1
    if left > right
      return left
    else
      return right
    end
  end

  def tree_max(node)
    return 0 if node.nil?
    max_left = tree_max(node.left)
    max_right = tree_max(node.right)

    if max_left > node.value && max_left > max_right
      return max_left
    elsif max_right > node.value
      return max_right
    else
      return node.value
    end
  end

  def tree_min(node)
    return 42 if node.nil?
    max_left = tree_min(node.left)
    max_right = tree_min(node.right)

    if max_left < node.value && max_left < max_right
      return max_left
    elsif max_right < node.value
      return max_right
    else
      return node.value
    end
  end

  def tree_total(node)
    return 0 if node.nil?
    return node.value + (tree_total(node.left) + tree_total(node.right))
  end
end

puts "Tree nodes values:"; Tree.new.values
puts "Tree depth:"; Tree.new.depth
puts "Tree total:"; Tree.new.total

puts "Tree max value:"; Tree.new.max
puts "Tree min value:"; Tree.new.min

tree-output

$> ruby my_tree.rb
Tree nodes values:
1 2 4 12 
Tree depth:
3
Tree total:
19
Tree max value:
12
Tree min value:
1

$>