Bytedance·Machine Learning Engineer·Technical Phone Screen·Senior

SeniorPrefer not to say

May 2026

Summary

Bytedance ML engineer interview that turned into more of a pure coding grind than I expected. They had me build the entire linked list scaffolding from scratch before even touching the actual problem, which ate up a chunk of time. Worth knowing if you're prepping for this loop.

Questions Asked (1)

Reverse the nodes of a linked list k at a time and return the modified list. Leftover nodes at the end (if fewer than k) stay in their original order. You cannot change node values, only relink the nodes themselves.

Algorithms & Data StructuresTechnical Trade-offs

Author's notes

Before I could even think about reversing anything, they asked me to write the node class, a helper to build a list from an array, and one to read it back.

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AI HintsAI Generated

Suggested Approach

First, clarify the problem constraints and edge cases, then propose an iterative solution that reverses k nodes at a time using pointer manipulation. Walk through the algorithm step-by-step, emphasizing how to track the previous group's tail and the next group's head to maintain connections. Finally, analyze time and space complexity and discuss potential optimizations or trade-offs.

Pro tip: Mention that you can avoid extra space by reversing in-place and that handling the final group requires checking if k nodes remain before reversing. Also, note that this problem tests pointer manipulation skills, which are crucial for optimizing ML pipelines and custom data loaders.

1. Clarify requirements and edge cases

Ask about input constraints (e.g., k value, list length) and confirm that leftover nodes stay in original order. Discuss edge cases like empty list, k=1, or k greater than list length.

2. Design the algorithm

Propose an iterative approach that processes the list in chunks of k. For each chunk, reverse the nodes and connect the previous chunk's tail to the new head, and the new tail to the next chunk's head.

3. Implement pointer manipulation

Use multiple pointers (prev, curr, next) to reverse each group. Keep track of the node before the current group (group_prev) and the node after k nodes (group_next) to reconnect properly.

4. Handle the final group

After reversing a group, check if there are at least k nodes left. If not, leave the remaining nodes as is and terminate.

5. Analyze complexity and trade-offs

State that time complexity is O(n) and space complexity is O(1). Discuss iterative vs recursive approaches, noting recursion uses O(n/k) stack space.

Key Points to Mention

In-place reversal without modifying node values
Tracking pointers to maintain connections between reversed groups
Handling the leftover nodes correctly
Time complexity O(n) and space complexity O(1)
Edge cases: k=1, k > list length, empty list
Iterative vs recursive trade-offs

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