Union-Find (Disjoint Set)

Union-Find (a disjoint-set structure) tracks which elements belong to the same group and merges groups in near-constant time. Use it for dynamic connectivity — counting components, detecting a cycle in an undirected graph, or grouping by equivalence.

6 LeetCode problems solved with the Union-Find (Disjoint Set) pattern. Practice them with spaced repetition so the pattern sticks.

• Accounts MergeMEDIUM · O(N*K*α(N) + N*K*log(N*K))
• Find Critical and Pseudo-Critical Edges in Minimum Spanning TreeHARD · O(E^2 * alpha(V))
• Graph Valid TreeMEDIUM · O(n + e)
• Greatest Common Divisor TraversalHARD · O(n + M log log M)
• Number of Connected Components in an Undirected GraphMEDIUM · O(E * alpha(N))
• Redundant ConnectionMEDIUM · O(n α(n))