如何修复此错误消息

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

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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