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Bytedance·Software Engineer·Technical Phone Screen·Intermediate

IntermediatePrefer not to say
Jun 2026

Summary

Bytedance coding interview, pretty standard linked list problem but they wanted both iterative and recursive solutions which tripped me up a bit on the spot.

Questions Asked (1)

Q1

Reverse a singly linked list and return the new head. Implement both an iterative solution using O(1) space and a recursive solution.

Algorithms & Data Structures
Author's notes

The iterative part was fine, three pointers, done.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the problem and edge cases, then walk through the iterative solution with three pointers (prev, curr, next), emphasizing O(1) space. Next, explain the recursive solution, highlighting the base case and the recursive step that reverses the rest of the list and adjusts pointers. Finally, compare both approaches in terms of time/space complexity and trade-offs.

Pro tip: During the recursive explanation, explicitly mention that the recursion uses O(n) stack space, which is often overlooked. Also, be prepared to discuss how to handle very long lists where recursion might cause stack overflow, showing awareness of practical constraints.

1. Clarify requirements and edge cases

Confirm the function signature, input/output, and constraints. Discuss edge cases like empty list, single node, and two nodes.

2. Iterative solution with three pointers

Explain initializing prev as null, curr as head, and iterating while curr is not null. In each iteration, store next node, reverse the link, and advance pointers.

3. Recursive solution

Describe the base case: if head is null or head.next is null, return head. Recursively reverse the rest, then set head.next.next = head and head.next = null.

4. Complexity analysis and comparison

State that both solutions run in O(n) time. Iterative uses O(1) space, while recursive uses O(n) stack space. Discuss trade-offs and when to prefer one over the other.

5. Test with examples

Walk through a simple example (e.g., 1->2->3->null) for both solutions to verify correctness and demonstrate understanding.

Key Points to Mention

  • Time complexity: O(n) for both iterative and recursive solutions.
  • Space complexity: iterative is O(1), recursive is O(n) due to call stack.
  • Edge cases: empty list, single node, and two nodes.
  • Pointer manipulation: careful ordering to avoid losing references.
  • Recursive base case and the step where the head's next pointer is set to null.
  • Potential stack overflow in recursive solution for large lists.

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.