leetcode: 110. Balanced Binary Tree

Given a binary tree, determine if it is height-balanced.

For this problem, a height-balanced binary tree is defined as:

a binary tree in which the depth of the two subtrees of every node never differ by more than 1.

Example 1:

Given the following tree [3,9,20,null,null,15,7]:

    3
   / \
  9  20
    /  \
   15   7
Return true.

Example 2:

Given the following tree [1,2,2,3,3,null,null,4,4]:

       1
      / \
     2   2
    / \
   3   3
  / \
 4   4
Return false.

class Solution():
    def isBalanced(self, root):
        if not root:
            return True
        else:
            return abs( self.height(root.left) - self.height(root.right) ) <= 1 \
                   and self.isBalanced(root.left) and self.isBalanced(root.right)
    def height(self, root):
        if not root:
            return 0
        else:
            return max( self.height(root.left), self.height(root.right) ) + 1