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Google·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
May 2026

Summary

Google SWE coding round, one question, pretty straightforward on the surface but there are a few edge cases worth thinking through.

Questions Asked (1)

Q1

Given a list of strings and a prefix string, return all words from the list that begin with that prefix.

Algorithms & Data Structures
Author's notes

Case sensitivity tripped me up for a second.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the problem constraints (e.g., input size, case sensitivity, whether the list is static or dynamic) and then propose a straightforward solution using a linear scan with a string prefix check. If the list is large or queries are frequent, discuss optimizing with a trie or sorting plus binary search to achieve better time complexity.

Pro tip: Mention that in real-world systems like search autocomplete, a trie is often used to handle prefix queries efficiently, but for a one-off query, a simple scan is acceptable—showing you can balance simplicity and performance.

1. Clarify requirements

Ask about input size, case sensitivity, whether the list is static or dynamic, and if multiple queries will be made. This determines the optimal approach.

2. Propose a baseline solution

Suggest iterating through the list and checking if each word starts with the prefix using a built-in method like startsWith. This is O(n * m) where m is prefix length.

3. Optimize for large or repeated queries

If the list is large or queries are frequent, propose building a trie for O(m + k) retrieval, or sorting the list and using binary search to find the range of words with the prefix.

4. Analyze complexity and trade-offs

Compare time and space complexity of each approach. Discuss when to use each based on constraints like memory, query frequency, and list size.

5. Handle edge cases

Consider empty prefix, empty list, no matches, and case sensitivity. Mention how to handle them in the chosen solution.

Key Points to Mention

  • Time and space complexity of the baseline linear scan approach
  • Trie data structure for efficient prefix matching
  • Sorting and binary search to find the prefix range
  • Edge cases: empty prefix, empty list, no matches, case sensitivity
  • Built-in string methods like startsWith and their implementation
  • Trade-offs between simplicity and performance for different scenarios

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