Knew what a trie was but blanked on the clean way to structure the node class.
Start by clarifying the requirements and constraints, then design the Trie using a node structure with children and an end-of-word flag. Implement insert, search, and startsWith by traversing the tree character by character, and analyze time and space complexity.
Pro tip: Mention that you can optimize memory by using a hash map for children instead of an array when the alphabet is large or sparse, and discuss trade-offs. Also, consider edge cases like empty strings and null inputs.
Ask about the character set (e.g., lowercase letters), expected operations, and any memory constraints. Confirm whether the Trie should support deletion or other operations.
Define a TrieNode class with a children data structure (array or hash map) and a boolean flag isEndOfWord. Explain your choice based on the alphabet size and memory considerations.
Iterate through each character of the word, creating new nodes as needed, and mark the last node as end of word. Discuss time complexity O(m) where m is word length.
For search, traverse the Trie and return true only if the entire word exists and the last node is marked as end of word. For startsWith, traverse and return true if the prefix path exists, regardless of end-of-word flag.
State time complexity O(m) for all operations and space complexity O(n*m) for n words of average length m. Discuss edge cases like empty string, null input, and non-alphabetic characters.
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