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Stripe·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
Jun 2026

Summary

Stripe SWE interview with a single coding question about validating a numeronym. Pretty niche problem and I wasn't sure how deep they wanted me to go with edge cases.

Questions Asked (1)

Q1

Write a function to validate whether a given string is a valid numeronym (e.g. 'i18n' or 'k8s').

Algorithms & Data Structures
Author's notes

I knew what a numeronym was which helped, but I second-guessed myself on the edge cases.

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AI HintsAI Generated

Suggested Approach

Clarify the definition of a numeronym: a string that starts with a letter, ends with a letter, and contains a number in between that represents the count of omitted characters. Then implement a validation function that checks these conditions, handling edge cases like single-letter strings, multiple numbers, and non-alphanumeric characters.

Pro tip: Discuss how to handle Unicode letters and whether the number should be a positive integer without leading zeros, showing attention to detail and real-world robustness.

1. Clarify requirements

Ask the interviewer to confirm the exact rules for a valid numeronym, such as whether the number must be greater than 0, whether leading zeros are allowed, and if only ASCII letters are considered.

2. Define validation rules

Formalize the conditions: the string must have at least 3 characters, start and end with a letter, and contain exactly one numeric sequence in the middle that represents the count of omitted characters.

3. Implement the function

Write a function that iterates through the string or uses regular expressions to check the pattern, ensuring that the numeric part is a valid positive integer and that no other characters are present.

4. Test with edge cases

Validate the function with examples like 'i18n' (valid), 'k8s' (valid), 'a1b' (valid), '1abc' (invalid), 'abc' (invalid), 'a0b' (invalid), and 'a12b3c' (invalid).

5. Analyze complexity

State that the time complexity is O(n) where n is the length of the string, and space complexity is O(1) if using iterative checks.

Key Points to Mention

  • Definition of a numeronym: letter + number + letter, where the number indicates omitted characters.
  • Edge cases: empty string, single character, multiple numbers, leading zeros, non-alphanumeric characters.
  • Use of regular expressions or manual iteration for validation.
  • Handling of Unicode letters if applicable.
  • Time and space complexity analysis.
  • Potential follow-up: generating a numeronym from a word.

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