← Fortinet Interview Insights

Fortinet·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
Apr 2026

Summary

Interviewed for a software engineering role at Fortinet and got a pretty standard linked list traversal problem. Nothing too wild, but it's the kind of question where you can overthink it if you're not careful.

Questions Asked (1)

Q1

Given the head of a singly linked list of integers, traverse the list and return the minimum value. The solution must run in O(n) time and use O(1) extra space.

Algorithms & Data Structures
Author's notes

Pretty straightforward once you just start writing.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the problem constraints and edge cases, then propose a single-pass traversal using a variable to track the minimum. Emphasize that this achieves O(n) time and O(1) space, and discuss potential pitfalls like empty lists.

Pro tip: Mention that you would handle the empty list case explicitly, either by returning a sentinel value or throwing an exception, depending on the requirements. This shows attention to detail and defensive programming.

1. Understand the problem

Restate the problem in your own words and ask clarifying questions about input constraints, edge cases (e.g., empty list, single node), and expected return type.

2. Outline the approach

Explain that you will traverse the list once, maintaining a variable initialized to the head's value, and update it whenever a smaller value is found.

3. Analyze complexity

State that the algorithm runs in O(n) time because each node is visited once, and uses O(1) extra space since only a few variables are needed.

4. Handle edge cases

Discuss how to handle an empty list (e.g., return null, throw an exception, or return a sentinel like Integer.MAX_VALUE) and confirm with the interviewer.

5. Code and test

Write clean code with meaningful variable names, then walk through a small example to verify correctness.

Key Points to Mention

  • Time complexity: O(n) because each node is visited exactly once.
  • Space complexity: O(1) because only a constant number of variables are used.
  • Edge cases: empty list, single node, all negative numbers, duplicates.
  • Initialization: set min to the head's value to avoid sentinel issues.
  • Traversal: use a while loop to iterate through the list.
  • Return type: ensure it matches the problem's specification (e.g., int).

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