Day 18 — Tries

What you’ll learn here

• Prefix trees: nodes, children pointers, the isEndOfWord flag
• The three core operations: insert, search, startsWith — each in O(L) where L is word length
• Real applications: autocomplete, spell-check, IP routing tables
• Compressed tries (radix trees) for when memory matters

Tries shine when your data is a set of strings sharing common prefixes. They make problems that look O(N·L) collapse to O(L).