如何修复此错误消息 [英] How do I fix this error message
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问题描述
作为我以前帖子的延续，有了帮助和建议，我已经成功编写了我的程序的一部分而没有错误，但是现在因为我正在尝试合并排序linkList我现在收到如下错误...
As a continuation to my previous posts with the help and advise given I have managed to code a good part of my program without errors, but right now as I am attempting to merge sort the linkedList I am now getting an error like below...
Traceback (most recent call last):
File "C:\Users\TP_baseline\Desktop\DSAG\ProjecTest4.py", line 124, in <module>
head -->
30 -->
20 -->
10 -->
End
ll.mergeSort()
File "C:\Users\TP_baseline\Desktop\DSAG\ProjecTest4.py", line 90, in mergeSort
l1, l2 = divideLists(head)
NameError: name 'divideLists' is not defined
我有什么试过：
我的现有代码如下：
What I have tried:
My Existing Code Is As Below..
class Node:
def __init__(self, val, next_ref):
self.val = val;
self.next = next_ref;
head= None;
class LinkedList:
def AddBookToFront(val):
global head;
new_node = Node(val, None)
new_node.next = head
head = new_node
# inserts new node at specific position in singly linked list.
def AddBookAtPosition(val, position):
global head;
current_node = head;
while(position > 1):
position -= 1;
current_node = current_node.next;
temp_next = current_node.next;
node = Node(val, temp_next);
current_node.next = node;
# prints singly linked list values.
def DisplayBook():
global head;
print("Single linked list");
current_node = head;
print ("head -->",);
while(current_node is not None):
print (current_node.val, "-->",);
current_node = current_node.next;
print ("End");
def RemoveBookAtPosition(position):
global head;
# If linked list is empty
if head == None:
return
# Store head node
temp = head
# If head needs to be removed
if position == 0:
head = temp.next
temp = None
return
# Find previous node of the node to be deleted
for i in range(position -1 ):
temp = temp.next
if temp is None:
break
# If position is more than number of nodes
if temp is None:
return
if temp.next is None:
return
# Node temp.next is the node to be deleted
# store pointer to the next of node to be deleted
next = temp.next.next
# Unlink the node from linked list
temp.next = None
temp.next = next
def mergeLists(l1, l2):
temp = None
if l1 is None:
return l2
if l2 is None:
return l1
if l1.data <= l2.data:
temp = l1
temp.next = mergeLists(l1.next, l2)
else:
temp = l2
temp.next = mergeLists(l1, l2.next)
return temp
# Defining function which will sort the linked list using mergeSort
def mergeSort():
global head;
if head is None or head.next is None:
return head
l1, l2 = divideLists(head)
l1 = mergeSort(l1)
l2 = mergeSort(l2)
head = mergeLists(l1, l2)
return head
# Defining function which will divide a linked list into two equal linked lists
def divideLists():
global head;
slow = head # slow is a pointer to reach the mid of linked list
fast = head # fast is a pointer to reach the end of the linked list
if fast:
fast = fast.next
while fast:
fast = fast.next # fast is incremented twice while slow is incremented once per loop
if fast:
fast = fast.next
slow = slow.next
mid = slow.next
slow.next = None
return head, mid
ll=LinkedList
ll.AddBookToFront(10);
ll.AddBookToFront(20);
ll.DisplayBook();
ll.AddBookToFront(30);
ll.DisplayBook();
ll.AddBookAtPosition(45, 2);
print ("After insert node at 2");
ll.DisplayBook();
ll.RemoveBookAtPosition(2)
print ("After removal of node @ 2nd position");
ll.DisplayBook();
ll.mergeSort()
如果有人能告诉我如何解决这个错误，我将不胜感激。 />
谢谢
I would be grateful if anyone could enlighten me on how to fix this error.
Thanks
推荐答案
在<$上方移动divideLists（）函数的定义c $ c> mergeSort（）定义它的使用位置。
你也在调用divideLists（）这里有一个参数
Move the definition of thedivideLists()function above themergeSort()definition where it is used.
You are also callingdivideLists()with an argument here
l1, l2 = divideLists(head)但函数定义不接受任何参数：
but the function definition does not accept any arguments:
def divideLists():因此要么将函数定义更改为接受一个参数，或者在没有 head 参数的情况下调用它。
So either change the function definition to accept an argument, or call it without the head parameter.
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