Reverse Linked List
As a Senior engineer, explain Reverse Linked List. What problem does it solve and how would you describe it in an interview?
Answers use simple, clear English.
Quick interview answer
At Senior depth: start with the problem, then mechanism, then a short example. Iterative: prev=None, curr=head; save next, point curr.next=prev, advance.
Detailed answer
At Senior depth: start with the problem, then mechanism, then a short example. Iterative: prev=None, curr=head; save next, point curr.next=prev, advance. Recursive variant uses head as new tail after reversing rest. Core: Iterative: prev=None, curr=head; save next, point curr.next=prev, advance. Recursive variant uses head as new tail after reversing rest. Real-time example: Undo stack in a text editor implemented as singly linked list needs in-place reversal for replay. Pros: O(n)/O(1) iterative; tests pointer discipline fundamentals. Cons: Recursive version O(n) stack; doubly linked needs both pointer updates. Common mistakes: Losing reference to next before rewiring; returning wrong node (old head vs new head). Best practices: Draw three pointers; return prev as new head after loop. Audience level: Senior.
Full explanation
Iterative: prev=None, curr=head; save next, point curr.next=prev, advance. Recursive variant uses head as new tail after reversing rest.
Real example & use case
Undo stack in a text editor implemented as singly linked list needs in-place reversal for replay.
Pros & cons
Pros: O(n)/O(1) iterative; tests pointer discipline fundamentals. Cons: Recursive version O(n) stack; doubly linked needs both pointer updates.
Common mistakes
Losing reference to next before rewiring; returning wrong node (old head vs new head).
Best practices
Draw three pointers; return prev as new head after loop.
Follow-up questions
- How would you test Reverse Linked List?
- What metrics prove Reverse Linked List is healthy in prod?
- How does Reverse Linked List change at 10× traffic?