Five rounds and they kept the coding portion pretty focused.
Start by clarifying the problem requirements and constraints, then explain the Trie structure and its advantages for prefix-based operations. Walk through the implementation step-by-step, discussing time and space complexity, and consider edge cases and potential optimizations.
Pro tip: Mention real-world applications of Tries, such as autocomplete or IP routing, to show practical understanding. Also, discuss memory optimization techniques like using a hash map for children or compressed Tries (radix trees) when appropriate.
Ask questions to understand the problem scope, input constraints, and expected operations (insert, search, startsWith, etc.). Confirm if the Trie should support deletion or other advanced features.
Explain the Trie node structure, typically with an array or hash map for children and a boolean flag for end-of-word. Discuss trade-offs between fixed-size arrays and dynamic structures.
Code the insert, search, and prefix search methods, ensuring correct traversal and flag updates. Handle edge cases like empty strings and null inputs.
State the time complexity for each operation (O(m) where m is key length) and space complexity (O(total characters * alphabet size) or O(total characters) with hash maps).
Walk through test cases, including normal and edge cases. Suggest optimizations like using a compressed Trie or limiting alphabet size if applicable.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.