# Definition for a binary tree node.

class TreeNode

attr_accessor :val, :left, :right

def initialize(val)

@val = val

@left, @right = nil, nil

end

end

# @param {TreeNode} root

# @return {Boolean}

def is_balanced(root)

if root.nil?

return true

end

l_height, l_balanced = subtree_height root.left

r_height, r_balanced = subtree_height root.right

unless l_balanced and r_balanced

return false

end

unless -1 <= l_height - r_height and l_height - r_height <= 1

return false

end

true

end

def subtree_height(node)

if node.nil?

return 0, true

end

leftHeight, leftBalanced = subtree_height node.left

rightHeight, rightBalanced = subtree_height node.right

unless leftBalanced and rightBalanced

return 0, false

end

balancedValue = leftHeight - rightHeight

balanced = if balancedValue < -1 or balancedValue > 1 then false else true end

unless balanced

return 0, false

end

maxHeight = if leftHeight > rightHeight then leftHeight else rightHeight end

return maxHeight + 1, true

end

root = TreeNode.new(1)

puts is_balanced root