CodeMosa

Master LeetCode Patterns

5 Problems

Union-Find (DSU) Practice Problems

Dynamic connectivity, Kruskal’s MST, and grouping via disjoint-set union with path compression.

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Relevant Patterns

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Study these pattern guides before tackling the problems. Understanding the core concepts will help you solve them more efficiently.
Union-Find (DSU)Minimum Spanning Tree

Practice Problems

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1
Number of Provinces
Medium#547
Show 2 hints
  • Union cities with edges; count unique roots at the end.
  • Alternatively BFS/DFS per component.
2
Redundant Connection
Medium#684
Show 2 hints
  • Return first edge forming a cycle while unioning.
  • Union‑by‑rank + path compression for near O(1).
3
Accounts Merge
Medium#721
Show 2 hints
  • Union accounts by shared emails; group by root and sort addresses.
  • Map email → id; careful with name grouping.
4
Most Stones Removed with Same Row or Column
Medium#947
Show 2 hints
  • Union by row/col keys; answer = n - number of components.
  • Coordinate compression on rows/cols to single DSU space.
5
Smallest String With Swaps
Medium#1202
Show 2 hints
  • Union index pairs; sort characters within each component and rebuild string.
  • Min‑heap per component to pop smallest letters.

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