How do you reverse a linked list in groups of size k?
This problem combines linked list manipulation with grouping logic. It tests iterative processing and pointer management skills in a non-trivial way.
Why Interviewers Ask This
Reversing in groups requires careful handling of partial lists and maintaining connections between groups. Interviewers assess the candidate's ability to manage complex pointer updates without losing references.
How to Answer This Question
Break the list into chunks of size K. Reverse each chunk individually using standard reversal logic. Connect the tail of the reversed chunk to the head of the next chunk. Handle the last group if it has fewer than K nodes by reversing it or leaving it as is based on requirements.
Key Points to Cover
- Identify K-sized segments
- Reverse each segment in place
- Connect segments properly
- Handle remaining nodes
Sample Answer
I would traverse the list and identify segments of K nodes. For each segment, I reverse the links using three pointers. After reversing, I connect the end of the previous segment to the new head of the current segment. If the final segment has fewer than K nodes, I typically leave it unchanged unless specified otherwise.
Common Mistakes to Avoid
- Losing the head of the list
- Incorrectly connecting reversed segments
- Failing to handle the last partial group
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