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Amplitude·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
Jun 2026

Summary

Amplitude software engineering interview with two coding problems back to back. The employee validation one had a sneaky follow-up that I wasn't fully ready for, and the snake game was more involved than it sounds.

Questions Asked (2)

Q1

Implement a function that validates a collection of employees against a set of business rules, where employees can have direct reports and validation must recurse through all descendants.

Algorithms & Data StructuresTechnical Trade-offs
Author's notes

The recursive part wasn't too bad once I mapped out the tree structure in my head.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the business rules and the employee data structure, then outline a recursive validation strategy that traverses the hierarchy. Discuss trade-offs between recursion and iteration, and how to handle cycles or shared reports.

Pro tip: Mention that you would validate each employee exactly once even if they appear under multiple managers, using a visited set to avoid redundant work and infinite loops.

1. Clarify requirements and data model

Ask about the specific business rules, the employee object structure (e.g., id, managerId, directReports), and whether the hierarchy is a tree or can have cycles.

2. Choose traversal strategy

Decide between recursive DFS or iterative BFS/DFS. Consider stack depth limits and whether to use a visited set to handle cycles or shared reports.

3. Design validation logic

Define how to apply each business rule to an employee and aggregate results. Decide whether to fail fast or collect all violations.

4. Implement and test

Write clean code with clear separation of traversal and validation. Test with edge cases: empty collection, single employee, deep hierarchy, cycles, and multiple roots.

5. Discuss trade-offs and optimizations

Talk about time/space complexity, memoization, parallelization, and how to handle large hierarchies or streaming data.

Key Points to Mention

  • Recursive DFS vs iterative BFS/DFS and their trade-offs (stack overflow, memory)
  • Handling cycles or shared direct reports with a visited set to avoid infinite loops
  • Time and space complexity: O(n) time, O(h) space for recursion (h = height)
  • Error handling: fail fast vs collect all violations, and how to report them
  • Business rule abstraction: using strategy pattern or list of validators for extensibility
  • Edge cases: empty input, single node, multiple roots, deep hierarchy

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

Q2

Implement a simplified Snake game on a 2D grid with directional keyboard input, wall collision detection, and apple consumption that grows the snake's length.

Algorithms & Data StructuresSystem Design
Author's notes

Knew this type of question existed but still underestimated the edge cases.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and constraints, then outline the core data structures (grid, snake body, apple position) and game loop. Implement movement, collision detection, and apple consumption, and discuss how to test and optimize the solution.

Pro tip: Use a deque (double-ended queue) for the snake body to achieve O(1) movement and growth, and consider edge cases like self-collision and rapid direction changes to show thoroughness.

1. Clarify Requirements

Ask about grid size, initial snake length, apple spawning rules, and whether self-collision or wrapping is allowed. Confirm input handling and game-over conditions.

2. Design Data Structures

Choose a 2D grid representation (e.g., boolean matrix or set of coordinates) and a deque for the snake body to efficiently add/remove segments. Track apple position and current direction.

3. Implement Game Loop

On each tick, compute the new head based on direction, check for wall collision, self-collision, and apple consumption. Update the snake body accordingly and handle game over.

4. Handle Input and Rendering

Map keyboard input to direction changes, ensuring no immediate reversal. Render the grid, snake, and apple using simple console output or a graphics library.

5. Test and Optimize

Write unit tests for movement, collision, and growth. Discuss time/space complexity and potential optimizations like using a circular buffer or spatial hashing.

Key Points to Mention

  • Use a deque for O(1) snake movement and growth.
  • Collision detection: check boundaries and snake body (excluding tail if it moves).
  • Apple consumption: increase length and spawn new apple at random empty cell.
  • Direction handling: prevent 180-degree turns and buffer inputs for smooth control.
  • Game loop timing: use a fixed tick rate for consistent speed.
  • Testing: cover edge cases like eating apple at wall, self-collision, and full grid.

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