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Bytedance·Software Engineer·Technical Phone Screen·Intermediate

Intermediate
May 2026

Summary

Bytedance SWE interview, got a classic grouping problem that I've seen a dozen times but still managed to second-guess myself on the implementation details.

Questions Asked (1)

Q1

Given an array of strings, group all the anagrams together and return the groups in any order.

Algorithms & Data StructuresTechnical Trade-offs
Author's notes

I knew this one.

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AI HintsAI Generated

Suggested Approach

Clarify the problem constraints (e.g., input size, character set) and discuss the trade-offs between sorting each string versus using a character count as a key. Then implement a hash map where the key represents the anagram signature and the value is a list of strings, and analyze the time and space complexity.

Pro tip: Mention that using a character count key can be more efficient than sorting for long strings, but be aware of potential hash collisions if not encoded properly. Also, discuss how to handle Unicode characters if relevant.

1. Clarify requirements and constraints

Ask about input size, character set (lowercase English letters?), and whether the output order matters. This shows attention to detail and helps choose the optimal approach.

2. Discuss possible approaches

Compare sorting each string (O(N * K log K)) versus counting characters (O(N * K)) and explain when each is preferable. Mention that both use a hash map.

3. Design the algorithm

Choose a key: either the sorted string or a string representation of character counts (e.g., '#2#1#0...'). Use a hash map to group strings by key.

4. Implement and test

Write clean code, handle edge cases (empty strings, single string), and walk through a small example to verify correctness.

5. Analyze complexity and trade-offs

State time and space complexity, and discuss any trade-offs (e.g., sorting is simpler but slower for long strings; counting is faster but requires encoding).

Key Points to Mention

  • Hash map with key as sorted string or character count signature
  • Time complexity: O(N * K log K) for sorting, O(N * K) for counting, where N is number of strings and K is max length
  • Space complexity: O(N * K) to store the groups
  • Handling of edge cases: empty strings, strings with same characters but different lengths? (Actually anagrams must have same length)
  • Trade-offs: sorting is simpler and works for any character set; counting is faster but needs a fixed character set and careful encoding
  • Potential follow-up: how to handle Unicode or very large strings

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