Advanced~2h
Tries & Prefix Trees in Data Structures & AlgorithmsInterview Readiness Check
Character-by-character prefix matching — autocomplete, word search, prefix counting.
prefixautocompleteinsert searchword searchtrie nodeisEnd
Learning path
Try a sample question
Implement autocomplete: given a dictionary of 100,000 words, when a user types 'app', return all words starting with 'app'. Trie vs HashMap — which is better?
A.Trie — all words sharing prefix 'app' are grouped under the same path. Traverse to the 'app' node, then DFS to collect all descendants. Prefix search is O(prefix_length + results).
B.HashMap — O(1) lookup per word
C.Binary search on a sorted word list — O(log n) to find first match
D.Inverted index — map each 3-letter prefix to its word list
Sign up free to take the full check and see the answer with an explanation.
What this module tests
- Conceptual understanding of tries & prefix trees fundamentals
- Trade-offs and design decisions in real system scenarios
- prefix and autocomplete — applied knowledge
- Interview-style reasoning and explanation quality
Free to start
Take the Tries & Prefix Trees check →
10 questions · Dimension scoring · AI coach feedback · Shareable result
Test your knowledge — free →No credit card · Takes 10–15 min
Frequently asked questions
- What does the Tries & Prefix Trees check test?
- The check covers character-by-character prefix matching — autocomplete, word search, prefix counting. Questions span beginner to advanced difficulty and test both conceptual understanding and practical trade-off reasoning.
- What keywords should I know for Tries & Prefix Trees?
- Key concepts include: prefix, autocomplete, insert search, word search, trie node, isEnd. These frequently appear in data structures & algorithms interviews at product and infrastructure companies.
- How many questions are in the check?
- Each check has 10 questions — a mix of MCQ and short-answer. You get scored by dimension (e.g., scalability, consistency) so you know exactly where to focus.
- How long does it take to study Tries & Prefix Trees?
- Most engineers spend around 2 hours on this module. The check itself takes about 10–15 minutes. You can retake it up to 3 times per day.
- What prerequisite knowledge do I need before Tries & Prefix Trees?
- Tries & Prefix Trees builds on Trees: DFS & Recursion. Complete those first for the best results.
- Is prefix, autocomplete, insert search covered?
- Yes. The Tries & Prefix Trees module covers prefix, autocomplete, insert search among other key concepts. The check includes questions that reflect real data structures & algorithms interview patterns.