Check if a binary tree is balanced or not.

is_height_balanced.rb

class Node
  attr_accessor :value, :left, :right
  def initialize(value)
    @value = value
  end
end

def is_height_balanced?(node)
  return true if node.nil?

  return (
    (height(node.left)-height(node.right)).abs <= 1) && 
    is_height_balanced?(node.left) &&
    is_height_balanced?(node.right)
  )
end

def height(node)
  return 0 if node.nil?
  
  return 1 + [height(node.left), height(node.right)].max
end