When would you use a Trie for prefix search?
Reported in Ubisoft European engineering loops. Data structure trade-off question for autocomplete and dictionary lookups.
Interview scenario
Context for Ubisoft candidates:
Design insert and startsWith operations for a large word dictionary.
Model answer
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A Trie stores characters along paths from root, marking end-of-word nodes. Prefix queries are fast because lookup follows characters directly rather than scanning all strings.
Insert and prefix search are O(L) where L is word length. Trade-off is memory overhead due to many node pointers, so compression techniques (radix trie) may be needed in large systems.
insert(word):
node = root
for ch in word:
node = node.children[ch] if missing create
node.isWord = true
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