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Amplitude·Software Engineer·Onsite - Coding / Algorithms·Intermediate

Intermediate
Apr 2026

Summary

Amplitude SE interview that was basically one meaty coding problem: implement Snake from scratch. More design-heavy than I expected for a coding round, since they wanted a full class structure and a real discussion about edge cases and complexity.

Questions Asked (1)

Q1

Implement the classic Snake game with a working board, movement logic, collision detection, apple spawning, and a clean API (move, getScore, isGameOver).

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

I started coding before thinking through the data structure and kind of backed myself into a corner using a plain list for the body.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and constraints, then design the data structures and API before coding. Implement the game logic incrementally, testing each component (movement, collision, apple spawning) as you go, and finally discuss trade-offs and potential optimizations.

Pro tip: Demonstrate testability by writing unit tests for core logic (e.g., movement, collision) and separate the game logic from rendering to make it more maintainable and extensible.

1. Clarify Requirements

Ask questions to understand the expected board size, movement rules (e.g., wrapping or wall collision), apple spawning behavior, and API details (e.g., move direction input, score increment).

2. Design Data Structures and API

Choose appropriate data structures: a deque for the snake body to efficiently add/remove segments, a set for O(1) collision checks, and variables for apple position, score, and game state. Define the public methods: move(direction), getScore(), isGameOver().

3. Implement Core Logic

Code the movement logic: update the snake's head based on direction, check for collisions with walls or itself, handle apple consumption (grow snake, increase score, spawn new apple), and update game over state.

4. Test and Validate

Write unit tests for key scenarios: normal movement, eating an apple, collision with wall, collision with self, and game over. Ensure the API behaves as expected.

5. Discuss Trade-offs and Extensions

Talk about design choices (e.g., deque vs. array, set vs. scanning), time/space complexity, and potential improvements like supporting multiple apples, obstacles, or a graphical interface.

Key Points to Mention

  • Use a deque (or linked list) for the snake body to achieve O(1) addition/removal of segments.
  • Use a set (or hash set) to store snake body positions for O(1) collision detection.
  • Handle apple spawning by randomly selecting an empty cell, ensuring it doesn't overlap with the snake.
  • Ensure the API is clean and intuitive: move(direction) updates state, getScore() returns current score, isGameOver() returns boolean.
  • Consider edge cases: snake length 1, board boundaries, invalid direction input (e.g., reversing direction).
  • Discuss time and space complexity: O(1) per move for updates, O(n) space for snake storage.

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