eBay·Software Engineer·Technical Phone Screen·Junior

Junior

Apr 2026

Summary

Short coding screen at eBay, one question about string manipulation. Pretty straightforward stuff, nothing that should trip you up if you know your basic built-ins.

Questions Asked (1)

Given a list of characters, find the difference between the count of uppercase and lowercase letters using built-in string methods.

Algorithms & Data Structures

Author's notes

Went fine.

Create a free account to read the full note

AI HintsAI Generated

Suggested Approach

Clarify the input format and expected output, then iterate through the list of characters, using built-in string methods like isupper() and islower() to count uppercase and lowercase letters. Compute the difference (uppercase count minus lowercase count) and return it, handling edge cases such as non-letter characters.

Pro tip: Mention that you would use a single pass for efficiency and discuss how to handle non-letter characters (e.g., digits, symbols) by ignoring them or clarifying with the interviewer. This shows attention to detail and practical coding maturity.

1. Clarify requirements

Ask whether the list contains only letters or also other characters, and confirm the expected output (e.g., absolute difference or signed difference).

2. Choose built-in methods

Select appropriate string methods such as isupper() and islower() to identify uppercase and lowercase letters, respectively.

3. Iterate and count

Loop through each character in the list, incrementing counters for uppercase and lowercase letters based on the method results.

4. Compute difference

Calculate the difference between the uppercase count and lowercase count, and return the result.

5. Test edge cases

Consider empty list, all uppercase, all lowercase, and mixed with non-letter characters to ensure correctness.

Key Points to Mention

Use of built-in string methods like isupper() and islower() for character classification.
Time complexity: O(n) where n is the number of characters, as each character is processed once.
Space complexity: O(1) additional space for counters.
Handling of non-letter characters: either ignore them or clarify with the interviewer.
Definition of difference: typically uppercase count minus lowercase count, but confirm if absolute difference is needed.
Potential use of Python's sum() with generator expression for concise code.

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