Reverse Linked List
Walk the list with three pointers and flip each arrow to face the other way.
Decision · step 2 of 11Singly Linked List: Reverse the list
Remember next (1), then flip 5's arrow to point back at null.
What you will see
Three pointers march; every arrow detaches and reattaches pointing the other way.
Cost
| Best | O(n) |
|---|---|
| Average | O(n) |
| Worst | O(n) |
| Space | O(1) |
Recursive variant uses O(n) stack.
How you work with it here
play it through, step one change at a time, scrub to any step, run it on your own input, predict what happens next, try operations in any order.
Screen readers: Each node announces its value and what it points to; each step announces the pointer change ("node 3 now points to node 5").
Reduced motion: Pointer arrows redraw in place with a brief emphasis instead of animating the detach and reattach.
Before this
Variants
- Iterative Three-pointer walk.
- Recursive Reverse the rest
Taught by the same lesson
Singly Linked List covers these too, in the same run.