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

IntermediatePending
Jul 2026Remote

Summary

Took the Roblox OA and now I'm sitting here second-guessing everything. The CodeSignal was surprisingly easy but the simulation problems, especially the Mars drone one, did some damage. Roblox really loves 2D arrays right now.

Questions Asked (3)

Q1

Factory simulation problem: navigate and manage a factory environment programmatically.

Algorithms & Data StructuresSystem Design
Author's notes

Spent a decent chunk of time on this one and I'm still not sure how I did.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the problem scope and constraints, then model the factory as a graph with nodes (machines, storage) and edges (conveyors, paths). Design a system that combines pathfinding (e.g., A*) for navigation and a scheduling algorithm for resource management, ensuring scalability and robustness.

Pro tip: Demonstrate awareness of real-world constraints like concurrency and fault tolerance, and discuss how you would test and monitor the simulation to ensure correctness and performance.

1. Clarify Requirements and Constraints

Ask questions to understand the factory layout, objectives (e.g., maximize throughput), and constraints (e.g., time, resources). Confirm input/output formats and performance expectations.

2. Model the Environment

Represent the factory as a graph with nodes for machines/storage and edges for paths. Define state variables (e.g., machine status, inventory) and transitions.

3. Design Algorithms

Choose pathfinding algorithms (e.g., A*, Dijkstra) for navigation and scheduling algorithms (e.g., priority queues, round-robin) for task allocation. Consider optimization techniques like caching or heuristics.

4. Implement and Simulate

Write modular code with clear interfaces. Simulate the factory step-by-step, handling events and updating state. Use appropriate data structures for efficiency.

5. Test and Optimize

Validate with unit tests and edge cases. Profile performance and optimize bottlenecks. Discuss scalability and potential improvements.

Key Points to Mention

  • Graph representation of the factory (nodes, edges, weights)
  • Pathfinding algorithms (A*, Dijkstra) and heuristics
  • Scheduling and resource allocation strategies
  • Concurrency and synchronization (if multiple agents)
  • Performance metrics (throughput, latency) and optimization
  • Testing strategies (unit tests, simulation scenarios)

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

Q2

Mars drone simulation: write functions to control a drone navigating across maps, then apply those functions under test conditions.

Algorithms & Data StructuresTechnical Trade-offs
Author's notes

This one hurt.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the problem: define the map representation, drone state, movement commands, and test conditions. Then design modular functions for navigation, obstacle avoidance, and pathfinding, and outline how you would test them with unit tests and edge cases. Emphasize clean code, algorithmic efficiency, and robustness.

Pro tip: Demonstrate test-driven development by writing tests first for each function, and discuss how you would simulate the drone's environment to validate behavior under various conditions. This shows you prioritize correctness and maintainability.

1. Clarify Requirements

Ask questions to understand the map format, drone capabilities, movement rules, and what 'test conditions' entail. Confirm expected inputs, outputs, and constraints.

2. Design Data Structures

Choose representations for the map (e.g., 2D grid, graph), drone state (position, direction, battery), and commands. Consider using classes or structs for clarity.

3. Implement Core Functions

Write functions for moving the drone, detecting obstacles, and finding paths (e.g., BFS, A*). Ensure functions are modular and handle edge cases like boundaries.

4. Apply Under Test Conditions

Simulate the drone's navigation using the functions, and write unit tests for each function. Test scenarios like empty maps, obstacles, and unreachable destinations.

5. Discuss Trade-offs

Explain choices like algorithm selection (BFS vs A*), memory vs speed, and how you would optimize for large maps. Mention potential improvements.

Key Points to Mention

  • Modular function design with clear responsibilities
  • Choice of pathfinding algorithm and its complexity
  • Handling edge cases and invalid inputs
  • Test-driven development and unit testing
  • Simulation of drone environment for validation
  • Trade-offs between different approaches (e.g., time vs space)

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

Q3

Matrix traversal or manipulation problem (two separate questions), with the second requiring optimization from a naive to a more efficient solution.

Algorithms & Data Structures
Author's notes

Easiest part of the whole thing.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the problem constraints and expected input/output for both matrix questions. For the first, implement a straightforward traversal or manipulation using nested loops, then for the second, identify inefficiencies (e.g., repeated scans) and optimize using techniques like in-place marking, boundary tracking, or dynamic programming. Communicate your thought process clearly, and test with edge cases like empty matrices or single rows/columns.

Pro tip: At Roblox, interviewers value clean, maintainable code and the ability to discuss trade-offs. After optimizing, briefly mention the time/space complexity improvement and any potential side effects (e.g., mutating input) to show you consider real-world impact.

1. Clarify requirements and constraints

Ask about matrix dimensions, data types, allowed auxiliary space, and whether the input can be modified. Confirm expected output format and edge cases.

2. Solve the first question with a simple approach

Implement a clear, correct solution using nested loops or standard traversal patterns. Explain the logic step-by-step and analyze time/space complexity.

3. Identify inefficiencies in the second question

For the second problem, start with a naive solution, then pinpoint bottlenecks such as repeated passes or excessive memory usage. Discuss potential optimization strategies.

4. Optimize and implement the efficient solution

Apply an optimized technique (e.g., in-place marking, boundary shrinking, or DP) and code it cleanly. Explain how it improves complexity and why it works.

5. Test and discuss trade-offs

Walk through test cases including edge cases, and compare the naive vs. optimized solutions in terms of time, space, and readability.

Key Points to Mention

  • Time and space complexity analysis for both naive and optimized solutions
  • Edge cases: empty matrix, 1xN or Nx1 matrices, non-square matrices
  • In-place manipulation techniques and their trade-offs (e.g., mutating input)
  • Boundary tracking or direction arrays for traversal problems
  • Dynamic programming or prefix sums for optimization if applicable
  • Clear communication of thought process and code readability

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