剑指offer题目：输入一棵二叉树，求该树的深度。从根结点到叶结点依次经过的结点（含根、叶结点）形成树的一条路径，最长路径的长度为树的深度。
思路：深度使用递归
# -*- coding:utf-8 -*-
# class TreeNode:
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution:
def TreeDepth(self, pRoot):
# write code here
if pRoot == None:
return 0
#递归函数,调用solution
leftDepth= Solution.TreeDepth(self,pRoot.left);
rightDepth= Solution.TreeDepth(self,pRoot.right);
if leftDepth>rightDepth:
return leftDepth+1
else: return rightDepth+1