Explain Implement Trie (Prefix Tree).

Short answer: Each node has children map/array[26] and an isEnd flag. insert/search/startsWith walk character by character. Tries shine for autocomplete and dictionary prefix queries.

Complexity

Time O(L) per operation (L = word length), Space O(total characters).

Common follow-ups

• Word Search II (Trie + backtracking)
• Replace Words

Ask if alphabet is lowercase English — array[26] is cleaner than Dictionary.