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Chime·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
Apr 2026

Summary

Chime software engineer interview with a browser history design problem. Pretty involved for a single question but they clearly wanted to see how you think through data structures and edge cases, not just whether you could code it up.

Questions Asked (1)

Q1

Design and implement a BrowserSession class that supports navigating to URLs, going back and forward through history by a given number of steps, and optionally checking if a URL was ever visited. Walk through your data structure choices and trade-offs.

Algorithms & Data StructuresSystem DesignTechnical Trade-offs
Author's notes

This is one of those problems that looks like a linked list exercise but actually has a bunch of subtle edge cases that'll trip you up if you're not careful.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and constraints, then propose a data structure that supports O(1) navigation and optional O(1) visited checks. Walk through the design, implement core methods, and discuss trade-offs between time and space complexity.

Pro tip: Mention that you would use a doubly linked list for history and a hash set for visited URLs, but also discuss the trade-off of using a dynamic array with an index pointer for simplicity. This shows you consider both optimal and practical solutions.

1. Clarify Requirements

Ask about expected operations, constraints (e.g., max history size, concurrency), and whether visited check is mandatory. This ensures you design the right solution.

2. Choose Data Structures

Propose a doubly linked list for history to allow O(1) back/forward navigation, and a hash set for visited URLs for O(1) lookup. Alternatively, consider a dynamic array with an index for simplicity.

3. Implement Core Methods

Write pseudocode for navigateTo(url), back(steps), forward(steps), and wasVisited(url). Handle edge cases like stepping beyond history bounds.

4. Analyze Trade-offs

Compare time and space complexity of your chosen structures. Discuss pros and cons: linked list vs array, hash set vs tree set, and memory overhead.

5. Test and Optimize

Walk through example scenarios, test edge cases, and suggest optimizations like caching or lazy deletion if needed.

Key Points to Mention

  • Time complexity: O(1) for navigation and visited check with linked list + hash set.
  • Space complexity: O(n) for history and visited set, where n is number of unique URLs.
  • Trade-offs: Array with index is simpler but back/forward may be O(1) if index adjusted; however, inserting new URL after going back truncates forward history.
  • Handling duplicate visits: visited set stores unique URLs; history may contain duplicates.
  • Edge cases: stepping back/forward beyond available steps, navigating to same URL, empty history.
  • Scalability: consider memory limits, persistence, and concurrency if needed.

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