Implement Trie Solution

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: $O(L)$ for all operations. Space: $O(\text{total characters across all words})$.