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Discord·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
May 2026

Summary

Got a coding question for a Data Engineer role at Discord that was basically a string manipulation problem dressed up with some case-sensitivity nuance. Short and focused, probably a technical screen.

Questions Asked (1)

Q1

Write a function that takes two strings and returns the words that appear in only one of them, preserving the original casing but treating words as case-insensitive for comparison purposes.

Algorithms & Data Structures
Author's notes

The case-insensitivity thing is what makes it non-trivial.

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AI HintsAI Generated

Suggested Approach

Clarify the definition of a 'word' (e.g., split on whitespace) and confirm that output should preserve original casing from the first occurrence. Use a hash map to track each word's lowercase form and its original casing, then compute the symmetric difference between the two sets.

Pro tip: Mention that you'd use a case-insensitive comparison by normalizing to lowercase, but store the original casing to return. Also, discuss handling duplicates: if a word appears multiple times in one string but not the other, it should still be returned once.

1. Clarify requirements

Ask about word delimiters (whitespace, punctuation), case sensitivity, and output format (order, duplicates). Confirm that words are case-insensitive for comparison but original casing is preserved.

2. Choose data structures

Use a hash map (dictionary) to map lowercase words to their original casing for each string. Alternatively, use sets for efficient symmetric difference, but keep a separate map for casing.

3. Process each string

Split each string into words, iterate through them, and populate the maps. For each word, store the lowercase version as key and the original word as value (first occurrence).

4. Compute symmetric difference

Find words that are in one map but not the other. Collect the original casing from the map where the word exists.

5. Return result

Return the list of words, ensuring no duplicates and preserving the original casing. Discuss order (e.g., order of appearance in first string then second).

Key Points to Mention

  • Case-insensitive comparison via lowercasing, but preserving original casing for output.
  • Handling duplicates: a word appearing multiple times in one string should only be returned once.
  • Efficient lookup using hash maps/sets for O(n) time complexity.
  • Definition of a word: splitting on whitespace, and possibly stripping punctuation.
  • Edge cases: empty strings, strings with only one word, words with different cases (e.g., 'Hello' vs 'hello').
  • Order of output: clarify if order matters; if not, any order is fine, but typically preserve order of first appearance.

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