Python Program to Reverse a Linked List without Recursion

This is a Python program to display the nodes of a linked list in reverse without using recursion.

The program creates a linked list using data items input from the user and displays it in reverse.

1. Create a class Node.
2. Create a class LinkedList.
3. Define methods append and display inside the class LinkedList to append data and display the linked list respectively.
4. Define the method display_reversed.
5. display_reversed uses the variable end_node to keep track of the last node that was printed. The variable current then iterates through the list until it reaches the node before end_node. That node is then displayed.
6. Create an instance of LinkedList, append data to it and display the list in reverse order.

Here is the source code of a Python program to display the nodes of a linked list in reverse without using recursion. The program output is shown below.

class Node:
    def __init__(self, data):
       self.data = data
       self.next = None
 
class LinkedList:
    def __init__(self):
        self.head = None
        self.last_node = None
 
    def append(self, data):
        if self.last_node is None:
            self.head = Node(data)
            self.last_node = self.head
        else:
            self.last_node.next = Node(data)
            self.last_node = self.last_node.next
 
    def display_reversed(self):
        end_node = None
 
        while end_node != self.head:
            current = self.head
            while current.next != end_node:
                current = current.next
            print(current.data, end = ' ')
            end_node = current
 
a_llist = LinkedList()
n = int(input('How many elements would you like to add? '))
for i in range(n):
    data = int(input('Enter data item: '))
    a_llist.append(data)
 
print('The reversed linked list: ', end = '')
a_llist.display_reversed()

1. An instance of LinkedList is created.
2. The user is asked for the number of elements they would like to add. This is stored in n.
3. Using a loop, data from the user is appended to the linked list n times.
4. The linked list is displayed in reverse by calling the method display_reversed.

Case 1:
How many elements would you like to add? 4
Enter data item: 7
Enter data item: 2
Enter data item: 1
Enter data item: 9
The reversed linked list: 9 1 2 7 
 
Case 2:
How many elements would you like to add? 1
Enter data item: 5
The reversed linked list: 5 
 
Case 3:
How many elements would you like to add? 2
Enter data item: 3
Enter data item: 1
The reversed linked list: 1 3

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