Implement the trie with all three operations. Design choices:
- Hash map vs. array for children: Hash map is flexible (any character set). Array is faster for fixed alphabets (constant-time child lookup).
- Separate class for node: Cleaner code, easier to extend with additional fields.
Testing checklist:
- Insert and search same word
- Search for prefix of existing word (should return false)
- startsWith for prefix of existing word (should return true)
- Search/startsWith for non-existent strings
Time: for all operations. Space: .