Maximum Depth of Binary Tree

　　　　这道题为简单题

　　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.

　　思路：

　　　　我是用递归做的，当然也可以用深搜和广搜，递归的话就是比较左右子树的深度然后返回

　　代码：

 1 # Definition for a binary tree node.
 2 # class TreeNode(object):
 3 #     def __init__(self, x):
 4 #         self.val = x
 5 #         self.left = None
 6 #         self.right = None
 7
 8 class Solution(object):
 9     def maxDepth(self, root):
10         """
11         :type root: TreeNode
12         :rtype: int
13         """
14         if not root: return 0
15
16         left = self.maxDepth(root.left)
17         right = self.maxDepth(root.right)
18         if left > right:
19             return 1 + left
20         else:
21             return 1 + right