Package org.jgrapht.alg.vertexcover
Class GreedyVCImpl<V,E>
- java.lang.Object
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- org.jgrapht.alg.vertexcover.GreedyVCImpl<V,E>
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- Type Parameters:
V
- the graph vertex typeE
- the graph edge type
- All Implemented Interfaces:
VertexCoverAlgorithm<V>
public class GreedyVCImpl<V,E> extends java.lang.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 usingClarksonTwoApproxVCImpl
.- Author:
- Joris Kinable
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Nested Class Summary
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Nested classes/interfaces inherited from interface org.jgrapht.alg.interfaces.VertexCoverAlgorithm
VertexCoverAlgorithm.VertexCover<V>, VertexCoverAlgorithm.VertexCoverImpl<V>
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Constructor Summary
Constructors Constructor Description GreedyVCImpl(Graph<V,E> graph)
Constructs a new GreedyVCImpl instance where all vertices have uniform weights.GreedyVCImpl(Graph<V,E> graph, java.util.Map<V,java.lang.Double> vertexWeightMap)
Constructs a new GreedyVCImpl instance
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description VertexCoverAlgorithm.VertexCover<V>
getVertexCover()
Finds a greedy solution to the minimum weighted vertex cover problem.
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Method Detail
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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 ratioweight(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 interfaceVertexCoverAlgorithm<V>
- Returns:
- greedy solution
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