Stripe·Software Engineer·Technical Phone Screen·Intermediate

Intermediate

Jun 2026

Summary

Stripe coding screen, pretty focused on low-level string/display logic rather than the usual algorithmic stuff. One question, not too long, but there are more moving pieces than you'd expect at first glance.

Questions Asked (1)

You're given a bitmap lookup table that maps each character to a 2D grid of pixels, where '#' is a lit pixel and ' ' is unlit. Write a function that takes a character, looks it up in the table, and prints its bitmap row by row. Cover how the table is structured, how you handle characters that aren't in the table, and how you emit each row.

Algorithms & Data StructuresTechnical Trade-offs

Author's notes

I went straight to the happy path and forgot about missing characters until the interviewer nudged me.

Create a free account to read the full note

AI HintsAI Generated

Suggested Approach

Start by clarifying the table structure and the expected output format, then walk through a simple lookup-and-print implementation. Discuss edge cases like missing characters and how to handle them gracefully, and mention any trade-offs in your design choices.

Pro tip: Mention that you'd consider caching or precomputing the bitmap rows if the function is called frequently, showing awareness of performance beyond the basic implementation.

1. Clarify requirements and assumptions

Ask about the table's data structure (e.g., dictionary mapping characters to 2D arrays), the output format (e.g., print each row as a string), and how to handle unknown characters (e.g., error, fallback, or skip).

2. Design the lookup and validation

Explain how you'll retrieve the bitmap for the given character, checking if it exists in the table. If not, decide on a consistent behavior such as printing a placeholder or raising an exception.

3. Implement row-by-row emission

Iterate over each row of the 2D grid, convert the row (e.g., list of '#' and ' ') into a string, and print it. Ensure each row is printed on a new line.

4. Discuss edge cases and trade-offs

Cover cases like empty bitmaps, characters with varying row lengths, and performance considerations (e.g., precomputing strings vs. on-the-fly conversion).

Key Points to Mention

Table structure: likely a hash map (dictionary) where keys are characters and values are 2D arrays (lists of lists) of '#' and ' '.
Handling missing characters: options include throwing an error, printing a default placeholder, or logging a warning; choose based on requirements.
Row emission: join each row's characters into a string and print; ensure newline after each row.
Performance: consider precomputing row strings if the function is called often, or using a string builder for efficiency.
Edge cases: empty bitmap, inconsistent row lengths, and characters not in the table.
Testing: verify with known characters and unknown ones to ensure correct behavior.

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