How do you reverse nodes of a linked list in groups of k?
PICTURE THIS: STACK VS QUEUE
StackLIFOlast in, first out
QueueFIFOfirst in, first out
Simple meaning
Count k nodes ahead
WHY — Linked List instead of guessing?
Why interviewers care about Linked List:
This is a process
question about Linked List.
Panels listen for order,
trade-offs, and what you would actually do on a DSA project - not buzzwords.
Stay structured
Name the idea, why it exists, then one short example.
Close cleanly
End with when you use it and one common pitfall.
STEPS — What happens step by step?
Before you speak the answer, walk the interviewer through these steps:
- 1Define it
Count k nodes ahead
- 2if fewer than k
remain, stop.
- 3Reverse that run in
place, attach it to the previous group's tail, and continue.
- 4Time is O(n) and
extra space is O(1).
- 5Recursion that reverses the
rest first is O(n/k) stack frames.
- 6Close
When you pick this over the alternative.
EXAMPLE — See it in action
Here's a short line you can speak, broken into clear beats:
Say this line
“Time is O(n) and extra space is O(1).”
Break into beats
TimeisOnandextra
Speaking order
2987408337471632900
Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.
Key takeaway
Count k nodes ahead if fewer than k remain, stop.