110. Balanced Binary Tree 是否为平衡二叉树

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.

 题意：判断一个二叉树是否为平衡二叉树（任意一个节点的左右子树的深度相差不大于1）

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
 
class Solution(object):
    def isBalanced(self, root):
        return self.check(root) != -1
 
    def check(self, root):
        if root is None:
            return 0
        left = self.check(root.left)
        right = self.check(root.right)
        if left == -1 or right == -1 or abs(left - right) > 1:
            return -1
        return 1 + max(left, right)

来自为知笔记(Wiz)