Package org.graphstream.algorithm

Class Kruskal

java.lang.Object
org.graphstream.algorithm.AbstractSpanningTree
org.graphstream.algorithm.Kruskal
All Implemented Interfaces:
Algorithm, SpanningTree
Direct Known Subclasses:
Prim
public class Kruskal
extends AbstractSpanningTree
Compute a spanning tree using the Kruskal algorithm.

Kruskal's algorithm is a greedy algorithm which allows to find a minimal spanning tree in a weighted connected graph. More informations on Wikipedia.

Example

The following example generates a graph with the Dorogovtsev-Mendes generator and then computes a spanning-tree using the Kruskal algorithm. The generator creates random weights for edges that will be used by the Kruskal algorithm. If no weight is present, algorithm considers that all weights are set to 1. When an edge is in the spanning tree, the algorithm will set its "ui.class" attribute to "intree", else the attribute is set to "notintree". According to the css stylesheet that is defined, spanning will be displayed with thick black lines while edges not in the spanning tree will be displayed with thin gray lines. 
 import org.graphstream.graph.Graph;
 import org.graphstream.graph.implementations.DefaultGraph;
 
 import org.graphstream.algorithm.Kruskal;
 import org.graphstream.algorithm.generator.DorogovtsevMendesGenerator;
 
 public class KruskalTest {
  
        public static void main(String .. args) {
                DorogovtsevMendesGenerator gen = new DorogovtsevMendesGenerator();
                Graph graph = new DefaultGraph("Kruskal Test");
 
        String css = "edge .notintree {size:1px;fill-color:gray;} " +
                                 "edge .intree {size:3px;fill-color:black;}";
  
                graph.addAttribute("ui.stylesheet", css);
                graph.display();
 
                gen.addEdgeAttribute("weight");
                gen.setEdgeAttributesRange(1, 100);
                gen.addSink(graph);
                gen.begin();
                for (int i = 0; i < 100 && gen.nextEvents(); i++)
                        ;
                gen.end();
 
                Kruskal kruskal = new Kruskal("ui.class", "intree", "notintree");
 
                kruskal.init(g);
                kruskal.compute();
  }
 }
See Also:
AbstractSpanningTree
Computational Complexity :
O(m log n) where m is the number of edges and n is the number of nodes of the graph
Scientific Reference :
Joseph. B. Kruskal: On the Shortest Spanning Subtree of a Graph and the Traveling Salesman Problem. In: Proceedings of the American Mathematical Society, Vol 7, No. 1 (Feb, 1956), pp. 48–50

  • Field Details

  • Constructor Details

    • Kruskal

      public Kruskal()
      Create a new Kruskal's algorithm. Uses the default weight attribute and does not tag the edges.

    • Kruskal

      public Kruskal​(String weightAttribute, String flagAttribute)
      Create a new Kruskal's algorithm. The value of the flag attribute is true for the tree edges and false for the non-tree edges.
      Parameters:
      weightAttribute - attribute used to compare edges
      flagAttribute - attribute used to set if an edge is in the spanning tree

    • Kruskal

      public Kruskal​(String flagAttribute, Object flagOn, Object flagOff)
      Create a new Kruskal's algorithm. Uses the default weight attribute.
      Parameters:
      flagAttribute - attribute used to set if an edge is in the spanning tree
      flagOn - value of the flagAttribute if edge is in the spanning tree
      flagOff - value of the flagAttribute if edge is not in the spanning tree

    • Kruskal

      public Kruskal​(String weightAttribute, String flagAttribute, Object flagOn, Object flagOff)
      Create a new Kruskal's algorithm.
      Parameters:
      weightAttribute - attribute used to compare edges
      flagAttribute - attribute used to set if an edge is in the spanning tree
      flagOn - value of the flagAttribute if edge is in the spanning tree
      flagOff - value of the flagAttribute if edge is not in the spanning tree

  • Method Details