Pattern

Union-Find (Disjoint Set Union)

5 problems in the roadmap use this pattern.

Redundant Connection Medium
in Advanced Graphs
Reported at: GoogleMicrosoft
Number of Operations to Make Network Connected Medium
in Advanced Graphs
Accounts Merge Medium
in Advanced Graphs
Reported at: MetaAppleGoogle+3
Most Stones Removed with Same Row or Column Medium
in Advanced Graphs
Satisfiability of Equality Equations Medium
in Advanced Graphs