如何遍历二进制搜索树中的字母顺序python? [英] How to traverse a binary search tree in alphabetical order python?
问题描述
我需要您的帮助,或者如果您可以给我建议.我真的很挣扎,有些帮助会是完美的,所以这就是我到目前为止所得到的;
I need your help or if you can give me advice. I'm really struggling and some help would be perfect, so this is what I got so far;
import BST, TreeNode
class Bibliography:
def __init__(self):
self.bibtree = BST()
def getReference(self,key):
"""Return the reference for the key, if it exists, otherwise None."""
theValue = self.bibtree.retrieveKey(key,self.bibtree.root)
if theValue == None:
return None
else:
return theValue.payload
def addReference(self, key, value):
"""Add the reference represented by key and value.
Assume the key does not exist in the bibliography.
"""
self.bibtree.insertNode(key, value)
def removeReference(self, key):
"""Remove the reference with this key.
Assume the key exists in the bibliography.
"""
self.bibtree.deleteNode(key)
def outputBibliography(self):
"""Return a string with all references in alphabetical order.
There must be an empty line after each reference
"""
return self.traverse(self.bibtree.root)
def traverse(self, aNode):
"""Return a string with the references in the subtree rooted at aNode.
The references should be ordered alphabetically,
with an empty line after each reference
and a space between each key and its value. See the test file.
"""
if aNode:
self.traverse(aNode.leftChild)
return str(aNode.key, aNode.payload, end='\n\n')
self.traverse(aNode.right)
当我进行测试时,以下功能不起作用,需要帮助.它将作为列表返回到此括号[]中,我不希望这样做.我也想要一个空白行,也不会发生这种情况.我不确定我在做什么错,如果您可以给我一些建议,这会有所帮助.
When I do the test the below function is not working and need help.It returns it as a list in this bracket [ ] and I do not want this. I also want a blank line and this does not happen either. I'm not to sure what I'm doing wrong, if you can give me some advise this will be helpful.
def traverse(self, aNode):
"""Return a string with the references in the subtree rooted at aNode.
The references should be ordered alphabetically,
with an empty line after each reference
and a space between each key and its value. See the test file.
"""
res = []
if aNode:
res = self.traverse(aNode.leftChild)
res.append(aNode.key + ' ' + aNode.payload + '\n\n')
res = res + self.traverse(aNode.rightChild)
return res
使用此代码的输出是:
['Adams, A (1991) Loves football\n\n', 'Marlow, C (1996) Loves cricket\n\n', 'Smith, I (1994) Does not play sports\n\n']
我想要这个输出:
Adams, A (1991) Loves football
Marlow, C (1996) Loves cricket
Smith, I (1994) Does not play sports
推荐答案
您仍然要串联列表,如res + self.traverse(aNode.rightChild)
所示.好的,不用管我以前对此的评论,即使有列表,也可以在其中得到O ^ 2,因为您正在全部复制它们.这样做
And you are concatenating lists anyways, as in res + self.traverse(aNode.rightChild)
. Ok, never mind my previous comments about this, you get O^2 there even with lists, because you are copying them all over. Just do this
def traverse(self, aNode):
res = ""
if aNode:
res = self.traverse(aNode.leftChild)
res += aNode.key + ' ' + aNode.payload + '\n\n'
res += self.traverse(aNode.rightChild)
return res
最后得到的是最后一个引用后的空白行,因此,这是该作业所说的更真实的实现:"...每个引用后都有一个空白行...". join()
只会在引用之间插入换行符,而不能在最后一个之后插入.
This ends up giving you an empty line after the last reference, so it is more literal implementation of what the assignment says: "... with an empty line after each reference ...". That join()
would only insert the newlines between references, and not after the last one.
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