剑指offer 二叉树的深度

# -*- coding: utf-8 -*-
"""
Created on Wed Apr 10 09:29:36 2019

@author: Administrator
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：采用递归的思路，遍历到子节点，再返回，返回期间计数值加1，再递归
"""

# -*- 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 not pRoot:                       #如果空节点就返回0
            return 0
                                            #若为叶子节点就返回1
        if pRoot and not pRoot.left and not pRoot.right:    
            return 1
        left = self.TreeDepth(pRoot.left)   #开始遍历左子树
        left += 1                           #遍历后计数加1
        right = self.TreeDepth(pRoot.right) #开始遍历右子树
        right += 1                          #遍历后计数加1
        return max(left,right)              #最终返回其最大的值
        
if __name__ == '__main__':
    solution = Solution()
    
    #1 2 3 4 5 6 7 8
    node = TreeNode(8)
    node_left = TreeNode(1)
    node_right = TreeNode(3)
    node_left.left = node
    root_left = TreeNode(2)
    root_left.left = node_left
    root_left.right = node_right
    
    node_left = TreeNode(5)
    node_right = TreeNode(7)
    root_right = TreeNode(6)
    root = TreeNode(4)
    root.left = root_left
    root_right.left = node_left
    root_right.right = node_right
    root.right = root_right
    
    depth = solution.TreeDepth(root)
    print('depth: ',depth)  #depth:  4