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Dropbox·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
Apr 2026

Summary

Dropbox coding screen for a software engineer role. The problem was a hangman-style game implementation, which sounds straightforward but has enough moving parts to trip you up if you're not careful about how you model state.

Questions Asked (1)

Q1

Implement a word-guessing game where one player picks a secret word and the other guesses letters one at a time. Each guess is either a hit (reveal all positions of that letter in the word) or a miss (add the letter to a misses list). Design the game state and a guess(letter) API.

API & IntegrationsAlgorithms & Data StructuresSystem Design
Author's notes

The example walkthrough they did at the start was actually helpful for pinning down the exact behavior.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and edge cases, then design a clean state model with a secret word, revealed positions, and a set of missed letters. Implement the guess(letter) API to efficiently check hits, update state, and return a structured result, discussing time/space complexity and potential extensions.

Pro tip: Demonstrate production awareness by discussing how to make the API idempotent and thread-safe, and how to persist or serialize game state for resumption—showing you think beyond the algorithm.

1. Clarify requirements and edge cases

Ask about input constraints (e.g., case sensitivity, non-alphabetic characters, repeated guesses) and define the expected behavior for hits, misses, and game completion.

2. Design the game state

Choose data structures to store the secret word, revealed positions (e.g., a boolean array or set), and missed letters (e.g., a set). Consider memory and lookup efficiency.

3. Implement the guess(letter) API

Write logic to check if the letter is in the word, update revealed positions or misses, and return a result object indicating hit/miss, updated state, and whether the game is won or lost.

4. Analyze complexity and test

State the time and space complexity of the guess operation, and walk through test cases including edge cases like guessing the same letter twice or winning/losing.

5. Discuss extensions and trade-offs

Mention potential improvements such as supporting multiple words, persistence, concurrency, or a more efficient data structure for large alphabets.

Key Points to Mention

  • Choice of data structures: set for misses, boolean array or set for revealed positions, and string for secret word.
  • Handling repeated guesses: should they be ignored, counted as misses, or return an error?
  • Return type of guess(letter): include hit/miss status, updated revealed word, remaining attempts, and game status.
  • Time complexity: O(n) for scanning the word to find positions, but can be optimized with a precomputed letter-to-positions map.
  • Edge cases: guessing a letter not in the alphabet, empty word, or all letters guessed.
  • Potential extensions: serialization for saving game state, thread safety for concurrent guesses, and supporting multiple players.

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