Stripe·Software Engineer·Technical Phone Screen·Intermediate

Intermediate

Apr 2026

Summary

Stripe coding screen for a software engineer role, pretty focused on data validation logic. Nothing flashy, just a clean implementation problem with some edge cases that could trip you up if you weren't paying attention.

Questions Asked (1)

Given a list of KYC records where each record is a list of field values, write a function to validate each record against two rules: no field can be empty after stripping whitespace, and the fifth column must be at most 50 characters. Return the records that pass both rules. Target time complexity is O(R * N).

Algorithms & Data StructuresTechnical Trade-offs

Author's notes

I got the basic structure pretty fast but fumbled on the edge cases.

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AI HintsAI Generated

Suggested Approach

Clarify the input format and edge cases, then propose a single-pass solution that checks each record's fields for emptiness and the fifth column's length. Emphasize that the O(R * N) complexity is optimal since every field must be inspected in the worst case.

Pro tip: Mention that you would strip whitespace once per field and reuse the stripped value for both checks to avoid redundant work, and discuss how to handle records with fewer than five columns.

1. Clarify requirements and edge cases

Ask about the data types of field values (strings only?), behavior for records with fewer than 5 columns, and whether the fifth column is 1-indexed or 0-indexed. Confirm that 'empty after stripping whitespace' applies to all fields.

2. Outline the algorithm

Propose iterating through each record once, and for each record, iterating through its fields. For each field, strip whitespace and check if empty; for the fifth field, also check length ≤ 50. If any check fails, skip the record.

3. Analyze complexity

Explain that the time complexity is O(R * N) because each field is visited at most once, and space complexity is O(R * N) for the output in the worst case (or O(1) extra if output is not counted).

4. Discuss trade-offs and optimizations

Mention that early termination within a record can save time on average, but worst-case remains O(R * N). Also note that stripping whitespace creates new strings, which may impact memory; consider if in-place checks are possible.

5. Write clean code

Implement the function with clear variable names, handle edge cases (e.g., missing fifth column), and include a brief test case to demonstrate correctness.

Key Points to Mention

Time complexity O(R * N) is optimal because every field must be examined in the worst case.
Use early termination within a record to skip remaining checks once a failure is found.
Strip whitespace once per field and reuse the result for both emptiness and length checks.
Handle records with fewer than five columns gracefully (e.g., treat as invalid or skip).
Consider memory implications of creating stripped strings; discuss potential in-place alternatives.
Validate assumptions about input types (e.g., all fields are strings) and indexing (0-based vs 1-based).

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