[Leetcode]@python 110. Balanced Binary Tree

题目链接

https://leetcode.com/problems/balanced-binary-tree/

题目原文

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.

题目大意

给定一棵二叉树，判断这棵树是否平衡二叉树（任意左右子树的高度差小于等于1）

解题思路

借用求书高度的函数，递归求解

代码

# 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 maxDepth(self, root):
        """
 :type root: TreeNode
 :rtype: int
 """
        if root == None:
            return 0
        else:
            return max(self.maxDepth(root.left) + 1, self.maxDepth(root.right) + 1)

    def isBalanced(self, root):
        """
 :type root: TreeNode
 :rtype: bool
 """
        if root == None:
            return True
        if abs(self.maxDepth(root.left) - self.maxDepth(root.right)) <= 1:
            return self.isBalanced(root.left) and self.isBalanced(root.right)
        else:
            return False