题目描述
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。
note：
注意递归里面的变量，全局变量和局部变量
1 # -*- coding:utf-8 -*-
2 # class TreeNode:
3 # def __init__(self, x):
4 # self.val = x
5 # self.left = None
6 # self.right = None
7 class Solution:
8 def TreeDepth(self, pRoot):
9 # write code here
10 if not pRoot:
11 return 0
12 if not pRoot.left and not pRoot.right: # 叶子节点返回1
13 return 1
14 return max(self.TreeDepth(pRoot.left) +1,self.TreeDepth(pRoot.right)+1)
15
16
下面这个代码，报错，right_d在赋值前是局部变量
# -*- 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:
return 0
if not pRoot.left and not pRoot.right:
return 1
if pRoot.left:
left_d = self.TreeDepth(pRoot.left) +1
if pRoot.right:
right_d = self.TreeDepth(pRoot.right)+1
return max(left_d,right_d)
修改成功（以下代码是正确的）
1 # -*- coding:utf-8 -*-
2 # class TreeNode:
3 # def __init__(self, x):
4 # self.val = x
5 # self.left = None
6 # self.right = None
7 class Solution:
8 def TreeDepth(self, pRoot):
9 # write code here
10 if not pRoot:
11 return 0
12 #if not pRoot.left and not pRoot.right:
13 # return 1
14 #if pRoot.left:
15 left_d = self.TreeDepth(pRoot.left) +1
16 #if pRoot.right:
17 right_d = self.TreeDepth(pRoot.right)+1
18 return max(left_d,right_d)