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Upstart·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
Jun 2026

Summary

Interviewed for a software engineer role at Upstart and got a coding question that looked trivial on the surface but had enough edge cases to trip you up if you weren't careful. The core concept clicked fast, but the implementation details were where things got messy.

Questions Asked (1)

Q1

Given a scrambled message and a list of valid words, decode the message by finding, for each scrambled token, the word in the list that is an anagram of that token. Output the fully decoded message.

Algorithms & Data StructuresTechnical Trade-offs
Author's notes

The approach came to me pretty quickly: sort the letters of each word in the list to build a lookup map, then do the same for each token in the scrambled input and check against the map.

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AI HintsAI Generated

Suggested Approach

Clarify the problem constraints (e.g., case sensitivity, duplicates, word list size) and then propose an efficient solution using a hash map from sorted word signatures to original words. For each scrambled token, sort its characters to form a key and look up the corresponding word, concatenating results to decode the message.

Pro tip: Mention that you would preprocess the word list into a hash map for O(1) lookups, and discuss trade-offs like memory usage versus speed, and how to handle multiple words with the same anagram (e.g., store a list or pick the first).

1. Clarify requirements and edge cases

Ask about input format, case sensitivity, duplicate words, and whether the scrambled tokens are guaranteed to have a match. Confirm output format (e.g., space-separated words).

2. Design the data structure

Propose building a hash map where keys are sorted character strings (anagram signatures) and values are the corresponding valid words. Discuss handling collisions (multiple words with same signature).

3. Process the scrambled message

Split the message into tokens, sort each token's characters to form a key, and look up the key in the hash map. If found, replace the token with the mapped word; otherwise, handle the error (e.g., leave as is or raise exception).

4. Analyze complexity and trade-offs

Explain time complexity: O(N * K log K) for preprocessing (N words of length K) and O(M * L log L) for decoding (M tokens of length L). Space complexity O(N * K). Discuss alternatives like counting character frequencies to avoid sorting.

5. Test and validate

Walk through a small example, test edge cases (empty message, no match, duplicate anagrams), and confirm the solution works as expected.

Key Points to Mention

  • Hash map with sorted string keys for O(1) average lookup
  • Time and space complexity analysis
  • Handling multiple valid anagrams (e.g., store list or choose first)
  • Edge cases: case sensitivity, punctuation, empty input
  • Alternative approach: character frequency count as key
  • Scalability considerations for large word lists

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