balanced.rb

# Definition for a binary tree node.
# class TreeNode
#     attr_accessor :val, :left, :right
#     def initialize(val = 0, left = nil, right = nil)
#         @val = val
#         @left = left
#         @right = right
#     end
# end
# @param {TreeNode} root
# @return {Boolean}

def height(root)
  if root.nil? 
    return 0
  end
  
  left_height = height(root.left)
  right_height = height(root.right)
  
  return 1 + [left_height, right_height].max
end

def is_balanced(root)
  if root.nil?
    return true
  end
  
  left_height = height(root.left)
  right_height = height(root.right)
  
    if (left_height - right_height).abs > 1
        return false
    else
        return is_balanced(root.left) && is_balanced(root.right)
    end
end