Reorder List
Middle by slow and fast, reverse the second half, weave first and second alternately.
Decision · step 2 of 10Rewiring a List: Reorder first, last, second, ...
Slow moves one node for every two of fast. Fast stops at 7, so slow is at 4: the first half is 1, 2, 3, 4, the second 5, 6, 7.
What you will see
Two halves zip together one node at a time.
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.
Before this
Taught by the same lesson
Rewiring a List covers these too, in the same run.