Kruskal Algorithm
What Is Kruskal’s Algorithm?
Kruskal’s Algorithm is a greedy algorithm used to find the Minimum Spanning Tree (MST) of a connected, undirected, weighted graph.
It builds the MST by selecting the smallest-weight edges first, ensuring no cycles are formed.
Why Use Kruskal’s Algorithm?
It guarantees the least total edge weight to connect all vertices.
Especially useful when the graph has sparse connections or edges are already sorted.
It’s simple and efficient for edge-centric problems.
Where to Use Kruskal’s Algorithm?
Network Design: Laying out cables or pipelines with minimal cost.
Road Systems: Connecting cities with shortest total distance.
Clustering Algorithms: In machine learning, for hierarchical clustering.
Electrical Grids: Designing efficient power distribution networks.
Key Steps in Kruskal’s Algorithm
Sort all edges by weight (ascending).
Initialize MST as an empty set.
Iterate through edges:
Add edge if it doesn’t form a cycle (using Union-Find).
Stop when MST has V-1 edges (where V = number of vertices).
Constraints
Graph must be connected, undirected, and weighted.
Cannot handle negative cycles, but can handle negative weights.
Requires Union-Find (Disjoint Set) for cycle detection.
Time Complexity
O(E log E) → Sorting edges dominates, where E = number of edges.
Union-Find operations are nearly constant time with path compression.
Space Complexity
O(V + E) → For storing edges and disjoint sets, where V = vertices.
These complexities hold across best, average, and worst cases due to the sorting step and disjoint-set operations.
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