Design autocomplete with Trie

Q: Design autocomplete with Trie

This is a Coding & Algorithms interview question from Google for Software Engineer roles. View the full question and solution on PracHub.

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Question

Design and implement an autocomplete service using a prefix tree (Trie). Support operations insert(word, weight), update(word, newWeight), delete(word), and topK(prefix, k) that returns the k highest-weight words sharing the prefix, breaking ties lexicographically. Assume lowercase English letters. Explain the data structures you maintain at each node to make topK efficient, analyze time and space complexity for each operation, and discuss trade-offs (e.g., storing heaps/lists at nodes vs. computing on demand). Dry-run your solution on: insert('cat', 5), insert('car', 3), insert('cart', 8), insert('dog', 2), topK('ca', 2), update('car', 9), topK('ca', 2), delete('cart'), topK('ca', 2).

Design autocomplete with Trie

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