# Definition for a binary tree node

# class TreeNode:

# def __init__(self, x):

# self.val = x

# self.left = None

# self.right = None

class Solution:

# @param root, a tree node

# @return a boolean

def isBalanced(self, root):

if root is None:

return True

else:

if self.isBalanced(root.left) and self.isBalanced(root.right):

return abs(self.depth(root.left) - self.depth(root.right)) <= 1

else:

return False

def depth(self, root):

if root is None:

return -1

else:

return max(self.depth(root.left), self.depth(root.right)) + 1