【LeetCode with Python】 110. Balanced Binary Tree

题目

原题页面：https://leetcode.com/problems/balanced-binary-tree/
本文地址：http://leetcode.xnerv.wang/balanced-binary-tree/
题目类型：Tree, Depth-first Search
难度评价：Easy
类似题目：(E) Maximum Depth of 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.

分析

判断一棵树是否高度平衡，即每个节点的左右子树高度相差不过1，参考BBT二叉平衡树或AVL的定义。还是用常见的二叉树递归回溯解法。

代码

class Solution:
    def checkBBT(self, root):
        if None == root:
            return True, 0
        isLeftBBT, leftDepth = self.checkBBT(root.left)
        isRightBBT, rightDepth = self.checkBBT(root.right)
        isBBT = isLeftBBT and isRightBBT and abs(leftDepth - rightDepth) <= 1
        depth = max(leftDepth, rightDepth) + 1
        return isBBT, depth

    # @param root, a tree node
    # @return a boolean
    def isBalanced(self, root):
        return self.checkBBT(root)[0]