faire·Software Engineer·Technical Phone Screen·Intermediate

Intermediate

Apr 2026

Summary

Faire coding interview for a software engineer role. One meaty algorithm question with a bunch of follow-ups baked in. The problem looked like a fun puzzle at first glance but the edge cases piled up fast.

Questions Asked (1)

Given a sentence with mixed casing and punctuation, and a dictionary mapping lowercase words to syllable counts, write a function that finds and returns the first valid haiku (5-7-5 syllable structure) as three lines formed from a contiguous sequence of words in the sentence. Return null if none exists. Discuss your approach, complexity, and edge cases like unknown words, apostrophes, and irregular spacing.

Algorithms & Data StructuresTechnical Trade-offs

Author's notes

I started with a sliding window idea and then they nudged me toward prefix sums which honestly made more sense once I drew it out.

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AI HintsAI Generated

Suggested Approach

First, normalize the sentence by extracting words and stripping punctuation while preserving apostrophes for syllable lookup. Then, compute prefix sums of syllable counts and use a sliding window or two-pointer technique to find the first contiguous sequence that matches 5-7-5 syllables, returning the three lines or null if none exists.

Pro tip: Clarify assumptions upfront: ask whether the dictionary is case-insensitive, how to handle unknown words (e.g., skip or return null), and whether punctuation should be ignored or treated as word boundaries. This shows attention to detail and avoids misalignment with the interviewer's expectations.

1. Clarify requirements and edge cases

Ask about dictionary lookup rules (case sensitivity, unknown words, apostrophes), punctuation handling, and whether the haiku must use all words or just a contiguous subsequence. Confirm return type (null vs. empty).

2. Preprocess the sentence

Tokenize the sentence into words, stripping punctuation but preserving apostrophes (e.g., 'don't' stays as one token). Convert each word to lowercase for dictionary lookup. Handle irregular spacing by splitting on whitespace.

3. Compute syllable counts and prefix sums

Map each token to its syllable count using the dictionary. If a word is unknown, decide on a fallback (e.g., skip the word, treat as 1 syllable, or return null). Build a prefix sum array for O(1) range sum queries.

4. Find the first valid 5-7-5 sequence

Use a sliding window or two-pointer approach: iterate over possible start indices, and for each, find the first end index where the syllable sum equals 5, then continue to find the next segment summing to 7, then 5. Return the first such triple as three lines.

5. Discuss complexity and edge cases

Analyze time complexity (O(n) with sliding window, O(n^2) naive) and space complexity (O(n) for prefix sums). Mention edge cases: empty sentence, no valid haiku, unknown words, punctuation, apostrophes, multiple spaces, and case sensitivity.

Key Points to Mention

Tokenization strategy: splitting on whitespace and stripping punctuation while preserving apostrophes for dictionary lookup.
Handling unknown words: options include skipping, treating as 1 syllable, or returning null; discuss trade-offs and ask for clarification.
Efficient search using prefix sums and sliding window to achieve O(n) time complexity.
Edge cases: empty input, no valid haiku, irregular spacing, mixed casing, punctuation, and apostrophes.
Return format: three lines as an array of strings, or null if no haiku found.
Potential ambiguity: whether the haiku must use all words or just a contiguous subsequence; clarify with interviewer.

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