LeetCode 104. Maximum Depth of Binary Tree

'''
Given a binary tree, find its maximum depth.
The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.
Note: A leaf is a node with no children.
'''

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    def maxDepth(self, root: 'TreeNode') -> 'int':
        if not root:
            return 0
        else:
            return 1 + max(self.maxDepth(root.left), self.maxDepth(root.right))