MathWorks·Software Engineer·Technical Phone Screen·Intermediate

IntermediatePrefer not to say

Apr 2026

Summary

Interviewed for a SET role at MathWorks and got a linked-list problem. Pretty standard stuff if you've seen it before, but there are enough variants that you can easily prepare for the wrong one.

Questions Asked (1)

Solve a two-pointer linked-list problem (e.g. detect a cycle, find the cycle's start, find the middle node, or return the k-th node from the end).

Algorithms & Data Structures

Author's notes

I went straight into cycle detection without asking which variant they wanted, which was a mistake.

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AI HintsAI Generated

Suggested Approach

Clarify the exact problem (cycle detection, cycle start, middle node, or k-th from end) and confirm constraints like list length and memory limits. Explain the two-pointer technique (slow/fast or lead/follow) and walk through the algorithm step-by-step, using a small example to illustrate. Analyze time and space complexity, and mention edge cases such as empty list, single node, or no cycle.

Pro tip: For cycle problems, emphasize that Floyd's algorithm uses O(1) space and explain the mathematical reasoning behind why the pointers meet at the cycle start. For k-th from end, mention the lead-follow approach and handle k > length gracefully.

1. Clarify the problem

Ask which specific two-pointer problem it is and confirm constraints (e.g., list length, memory limits, whether modification is allowed).

2. Choose the right two-pointer strategy

For cycle detection/start, use slow and fast pointers; for middle node, use slow and fast; for k-th from end, use lead and follow pointers with a gap of k.

3. Walk through the algorithm

Explain step-by-step how pointers move and what conditions terminate the loop. Use a small example to illustrate.

4. Analyze complexity and edge cases

State time and space complexity (usually O(n) time, O(1) space) and discuss edge cases like empty list, single node, no cycle, or k out of bounds.

5. Discuss extensions or optimizations

Mention alternative approaches (e.g., hash set for cycle detection) and trade-offs, or how to adapt if the list is doubly linked or if you need to return the node itself.

Key Points to Mention

Floyd's cycle-finding algorithm (tortoise and hare) and its O(1) space advantage
Mathematical proof for why the meeting point leads to the cycle start (distance from head to cycle start equals distance from meeting point to cycle start)
Lead-follow technique for k-th node from end: advance lead by k, then move both until lead reaches end
Slow and fast pointer technique for finding middle node: fast moves twice as fast as slow
Handling edge cases: empty list, single node, no cycle, k > length
Time complexity O(n) and space complexity O(1) for all these two-pointer solutions

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