Linked list reverse

Question

How can this code be best modified to reverse a doubly linked list while ensuring that both “next”and “prev” pointers are appropriately updated during the reversal process.

https://code.sololearn.com/ckORoit1CZJU/?ref=app

Answer 1

Izaiah Kay ,

Yeah. Update head inside loop. (No pun intended.)

https://sololearn.com/compiler-playground/ctFdIvFNzcOF/?ref=app

Answer 2

I don't understand your code at line 13 14 15 why you doing it "current.next = prev"
And prev = current
I think you may rewrite your code with code scheme.

Answer 3

Muhammadrizo

next_node = current.next
Saves the next node in the original list before the reversal.
current.next = prev
Adjusts the next pointer of the current node to point to the previous node, reversing the direction.
prev = current:
Moves the prev pointer to the current node for the next iteration.
current = next_node:
Moves the current pointer to the next node in the original list for the next iteration.

Answer 4

Izaiah Kay ,

If I wanted to reverse a doubly linked list, I would swap previous and next for each member in the list.

Python makes it easy to swap the values of two variables without creating any new variables.

a, b = 5, 10
a, b = b, a
print(a, b) # 10, 5

Why doesn't your class Node have a prev attribute?

Answer 5

Rain because initially The prev variable is used to keep track of the previous node as you traverse the list and reverse the next pointers assigning it in later stages

Answer 6

Rain ohh😅, sorry i didnt get it at first.
First check this one out and see

https://code.sololearn.com/cWh97u17c64E/?ref=app

Answer 7

Rain I see, looked through it but 😅 head is boiling now. Any ideas ?

Answer 8

Izaiah Kay ,

With only current and next, I believe that would support a linked list, not a doubly linked list.

Answer 9

Rain exactly, thats why i need help to modify it or rewrite it if need be

Answer 10

Izaiah Kay ,

Heh. We just went in a circle. My advice is to add a previous attribute to your Node class as a first step. Then you'll be able to create objects capable of assembling into a doubly linked list (which you'll need before you can reverse it).

Answer 11

Izaiah Kay ,

Getting fun. I tested it. It currently fails at line 22.

https://sololearn.com/compiler-playground/ciUtz6W4nrP1/?ref=app