Advanced~2h
Union Find / DSU in Data Structures & AlgorithmsInterview Readiness Check
Disjoint sets with path compression — group membership, cycle detection, Kruskal's MST.
disjoint setspath compressionunion by rankcycle undirectedconnected components
Learning path
Try a sample question
Given n people and a list of friend pairs, determine if person A and person B are in the same friend group (transitive friendship). Which data structure answers this efficiently with many updates?
A.BFS/DFS on an adjacency list — O(V + E) per query
B.Sorted array of friend pairs — binary search for connections
C.HashMap mapping each person to their friend set
D.Union-Find (Disjoint Set Union) — union(a, b) merges groups, find(a) returns group representative. After all unions, find(A) == find(B) iff same group. O(α(n)) ≈ O(1) per operation.
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What this module tests
- Conceptual understanding of union find / dsu fundamentals
- Trade-offs and design decisions in real system scenarios
- disjoint sets and path compression — applied knowledge
- Interview-style reasoning and explanation quality
Free to start
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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 Union Find / DSU check test?
- The check covers disjoint sets with path compression — group membership, cycle detection, kruskal's mst. Questions span beginner to advanced difficulty and test both conceptual understanding and practical trade-off reasoning.
- What keywords should I know for Union Find / DSU?
- Key concepts include: disjoint sets, path compression, union by rank, cycle undirected, connected components. 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 Union Find / DSU?
- 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 Union Find / DSU?
- Union Find / DSU builds on Graph Algorithms. Complete those first for the best results.
- Is disjoint sets, path compression, union by rank covered?
- Yes. The Union Find / DSU module covers disjoint sets, path compression, union by rank among other key concepts. The check includes questions that reflect real data structures & algorithms interview patterns.