# Definition for a binary tree node.

class TreeNode:

def __init__(self, x):

self.val = x

self.left = None

self.right = None

class Solution:

# https://leetcode-cn.com/problems/maximum-depth-of-binary-tree/

def maxDepth(self, root: TreeNode) -> int:

if not root:

return 0

leftDepth = self.maxDepth(root.left)

rightDepth = self.maxDepth(root.right)

depth = (leftDepth if leftDepth > rightDepth else rightDepth) + 1

return depth