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Circle·Software Engineer·Online Assessment (OA)·Intermediate

Intermediate
Apr 2026

Summary

Did a coding round for a Software Engineer role at Circle. It was a Level 1 task management problem, nothing algorithmically tricky, just more boilerplate than I expected for the time given.

Questions Asked (1)

Q1

Build a Task class that supports adding tasks and retrieving the current list of tasks, with formatted output.

Algorithms & Data StructuresTechnical Trade-offs
Author's notes

Pretty straightforward class design exercise.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements: what fields a task has, how tasks are stored, and what 'formatted output' means. Then design a simple Task class with an internal collection (e.g., list) and methods to add tasks and retrieve them, ensuring clean separation of concerns. Finally, implement formatted output via a __str__ or dedicated method, and discuss trade-offs like mutability, ordering, and extensibility.

Pro tip: Mention that you'd use a list for O(1) append and preserve insertion order, but if frequent lookups or uniqueness are needed, a dict keyed by task ID might be better. Also, encapsulate the task list to prevent external mutation, returning a copy or read-only view.

1. Clarify requirements

Ask about task attributes (e.g., id, title, status), expected operations (add, list, maybe remove/update), and the desired format for output (e.g., string, JSON, table).

2. Design the Task class

Define the class with an internal data structure (e.g., list) to store tasks, and methods like add_task and get_tasks. Consider whether tasks are represented as dicts, tuples, or separate objects.

3. Implement formatted output

Override __str__ or provide a method like format_tasks that returns a human-readable string, such as one task per line with aligned columns or bullet points.

4. Discuss trade-offs and edge cases

Talk about time complexity of operations, thread safety, persistence, and how to handle invalid input or empty task lists.

5. Test and iterate

Mention writing unit tests for adding tasks, retrieving them, and formatting output, and be prepared to extend the design if requirements change.

Key Points to Mention

  • Encapsulation: keep the task list private and expose controlled access via methods.
  • Data structure choice: list for ordered collection vs. dict for fast lookup by ID.
  • Formatted output: use __str__ for debugging or a dedicated method for user-facing display.
  • Immutability: return a copy of the task list to prevent unintended modifications.
  • Extensibility: design for future features like task removal, filtering, or persistence.
  • Time complexity: O(1) append for list, O(n) for retrieval if returning all tasks.

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