Module org.jgrapht.core
Package org.jgrapht.alg.vertexcover

Class GreedyVCImpl<V,E>

java.lang.Object
org.jgrapht.alg.vertexcover.GreedyVCImpl<V,E>
Type Parameters:
V - the graph vertex type
E - the graph edge type
All Implemented Interfaces:
VertexCoverAlgorithm<V>
public class GreedyVCImpl<V,E> extends Object implements VertexCoverAlgorithm<V>
Greedy algorithm to find a vertex cover for a graph. A vertex cover is a set of vertices that touches all the edges in the graph. The graph's vertex set is a trivial cover. However, a minimal vertex set (or at least an approximation for it) is usually desired. Finding a true minimal vertex cover is an NP-Complete problem. For more on the vertex cover problem, see http://mathworld.wolfram.com/VertexCover.html Note: this class supports pseudo-graphs Runtime: $O(|E| \log |V|)$ This class produces often, but not always, better solutions than the 2-approximation algorithms. Nevertheless, there are instances where the solution is significantly worse. In those cases, consider using ClarksonTwoApproxVCImpl.
Author:
Joris Kinable

  • Constructor Details

    • GreedyVCImpl

      public GreedyVCImpl(Graph<V,E> graph)
      Constructs a new GreedyVCImpl instance where all vertices have uniform weights.
      Parameters:
      graph - input graph

    • GreedyVCImpl

      public GreedyVCImpl(Graph<V,E> graph, Map<V,Double> vertexWeightMap)
      Constructs a new GreedyVCImpl instance
      Parameters:
      graph - input graph
      vertexWeightMap - mapping of vertex weights

  • Method Details

    • getVertexCover

      public VertexCoverAlgorithm.VertexCover<V> getVertexCover()
      Finds a greedy solution to the minimum weighted vertex cover problem. At each iteration, the algorithm picks the vertex v with the smallest ratio weight(v)/degree(v) and adds it to the cover. Next vertex v and all edges incident to it are removed. The process repeats until all vertices are covered. Runtime: O(|E|*log|V|)
      Specified by:
      getVertexCover in interface VertexCoverAlgorithm<V>
      Returns:
      greedy solution