在 Python 中计算二叉树的深度 [英] calculating depth of a binary tree in Python
问题描述
我是编程新手,正在尝试用 Python 计算二叉树的深度.我相信我的错误是因为 depth 是 Node 类的方法而不是常规函数.我正在尝试学习 OOP 并希望使用一种方法.这可能是新手错误...这是我的代码:
I am new to programming and am trying to calculate the depth of a binary tree in Python . I believe that my error is because depth is a method of the Node class and not a regular function. I am trying to learn OOP and was hoping to use a method. This might be a newbie error... Here is my code:
class Node:
def __init__(self, item, left=None, right=None):
"""(Node, object, Node, Node) -> NoneType
Initialize this node to store item and have children left and right.
"""
self.item = item
self.left = left
self.right = right
def depth(self):
if self.left == None and self.right == None:
return 1
return max(depth(self.left), depth(self.right)) + 1
i receive this error:
>>>b = Node(100)
>>>b.depth()
1
>>>a = Node(1, Node(2), Node(3))
>>>a.depth()
Traceback (most recent call last):
File "C:\Program Files\Wing IDE 101 4.1\src\debug\tserver\_sandbox.py", line 1, in <module>
# Used internally for debug sandbox under external interpreter
File "C:\Program Files\Wing IDE 101 4.1\src\debug\tserver\_sandbox.py", line 15, in depth
builtins.NameError: global name 'depth' is not defined
推荐答案
def depth(self):
if self.left == None and self.right == None:
return 1
return max(depth(self.left), depth(self.right)) + 1
应该是
def depth(self):
return max(self.left.depth() if self.left else 0, self.right.depth() if self.right else 0) + 1
更易读的版本:
def depth(self):
left_depth = self.left.depth() if self.left else 0
right_depth = self.right.depth() if self.right else 0
return max(left_depth, right_depth) + 1
问题是没有函数depth
.它是 Node
对象的一个方法,因此您需要从对象本身(左右)调用它.我将代码缩短为 self.left.depth() if self.left else 0
和 self.right.depth() if self.right else 0
以删除您以前拥有的检查(它们现在是隐式的),因为我相信完全有可能左边是 None
而右边是 Node
,反之亦然,这会导致原始代码抛出 AttributeError
因为 None
没有方法 depth
.
The issue is that there is no function depth
. It's a method of the Node
object, so you would need to call it from the object itself (left and right). I shortened the code to self.left.depth() if self.left else 0
and self.right.depth() if self.right else 0
in order to remove the checks you previously have (they're implicit now) since I believe it is entirely possible that the left is None
while the right is a Node
or vice versa, which would cause the original code to throw an AttributeError
since None
does not have a method depth
.
编辑
回答关于
块:
该行给出
如果
为真-y(视为真),并且
code> if
is false-y (视为 false)
The line gives <something>
if <some condition>
is true-y (treated as true), and <otherwise>
if <some condition>
is false-y (treated as false)
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