Leetcode 104 Maximum Depth of Binary Tree python

题目：

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.

求二叉树的深度，递归一下就可以求到了。

python新手(我)发现python中没有三元运算符，不过可以用true_part if condition else false_part模拟。虽然我后面用max函数代替了三元运算符，也实现了功能。

 class Solution(object):
     def maxDepth(self, root):
         if (root == None):
             return 0
         left_depth = self.maxDepth(root.left)
         right_depth = self.maxDepth(root.right)
         return max(left_depth, right_depth) + 1