Reverse in Groups of k
Count k ahead, reverse that run with prev and curr, hook the previous group's tail onto the new front.
Decision · step 2 of 13Rewiring a List: Groups of 3 with a short tail
From 1, count 3 ahead: 1, 2, 3 is a full group, ending before 4. Reverse it.
What you will see
One block reverses at a time; its tail reattaches to the next block's head.
Cost
| Best | O(n) |
|---|---|
| Average | O(n) |
| Worst | O(n) |
| Space | O(1) |
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.