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Upstart·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
Apr 2026

Summary

Got a coding question at Upstart for a software engineer role that was more interesting than your typical string manipulation problem. The anagram decoding twist with a shared first/last character constraint made it a step above the usual.

Questions Asked (1)

Q1

Given a vocabulary list and a string of scrambled words, decode the string. Each scrambled word is an anagram of exactly one vocabulary word and shares the same first and last character with it. Return the decoded string.

Algorithms & Data Structures
Author's notes

My first instinct was to just sort the characters of each word and use that as a lookup key, which works until it doesn't.

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AI HintsAI Generated

Suggested Approach

Clarify the problem constraints and edge cases, then propose an efficient algorithm using a hash map keyed by first and last characters to group vocabulary words. For each scrambled word, extract its first and last characters, retrieve the candidate group, and find the anagram by comparing sorted characters or character counts.

Pro tip: Mention that you can preprocess the vocabulary once to build the index, making each subsequent decode O(1) on average, and discuss how to handle duplicate anagrams or multiple matches by using additional constraints or returning any valid match.

1. Clarify requirements and edge cases

Ask about input size, whether vocabulary words are unique, if scrambled words are guaranteed to have exactly one match, and how to handle case sensitivity or non-alphabetic characters.

2. Design the data structure

Propose a hash map where keys are pairs of first and last characters (e.g., a tuple or a combined string) and values are lists of vocabulary words sharing those endpoints.

3. Preprocess the vocabulary

Iterate through the vocabulary list, compute the key for each word, and append the word to the corresponding list in the map.

4. Decode each scrambled word

For each scrambled word, compute its key, retrieve the candidate list, and find the anagram by comparing sorted characters or character frequency counts.

5. Analyze complexity and optimize

State the time and space complexity: O(V * L) preprocessing, O(S * L) decoding, where V and S are vocabulary and scrambled word counts, and L is average word length. Suggest optimizations like using character count arrays for faster anagram checks.

Key Points to Mention

  • Hash map keyed by first and last characters to narrow down candidates efficiently.
  • Anagram detection using sorted strings or character frequency counts.
  • Handling edge cases: empty strings, single-character words, no match found.
  • Time and space complexity analysis and potential optimizations.
  • Preprocessing the vocabulary once for multiple queries.
  • Clarifying assumptions about input guarantees and output format.

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