Balanced Binary Tree

题目描述

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.

解题方法

这一题也是用recursive的方法做

• 对于每一个root,分别get左右两边子树的max depth
• 如果balanced，就继续recursive的检查左右子树

Solution

# 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):
        """
        :type root: TreeNode
        :rtype: bool
        """
        if not root:
            return True
        leftDepth = self.getDepth(root.left)
        rightDepth = self.getDepth(root.right)
        diff = abs(leftDepth - rightDepth)
        if diff > 1:
            return False
        else:
            return self.isBalanced(root.left) and self.isBalanced(root.right)

    def getDepth(self, root):
        if not root:
            return 0
        return 1 + max(self.getDepth(root.left), self.getDepth(root.right))

Reference