/// <summary> Finds a greedy approximation for a minimal vertex cover of a specified
/// graph. At each iteration, the algorithm picks the vertex with the
/// highest degree and adds it to the cover, until all edges are covered.
///
/// <p>
/// The algorithm works on undirected graphs, but can also work on directed
/// graphs when their edge-directions are ignored. To ignore edge
/// directions you can use {@link
/// org._3pq.jgrapht.GraphHelper#undirectedGraph(Graph)} or {@link
/// org._3pq.jgrapht.graph.AsUndirectedGraph}.
/// </p>
///
/// </summary>
/// <param name="g">the graph for which vertex cover approximation is to be found.
///
/// </param>
/// <returns> a set of vertices which is a vertex cover for the specified
/// graph.
/// </returns>
public virtual SupportClass.SetSupport findGreedyCover(UndirectedGraph g)
{
// C <-- {}
//UPGRADE_TODO: Class 'java.util.HashSet' was converted to 'SupportClass.HashSetSupport' which has a different behavior. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1073_javautilHashSet'"
SupportClass.SetSupport cover = new SupportClass.HashSetSupport();
// G' <-- G
UndirectedGraph sg = new UndirectedSubgraph(g, null, null);
// compare vertices in descending order of degree
VertexDegreeComparator comp = new VertexDegreeComparator(sg);
// while G' != {}
while (sg.edgeSet().Count > 0)
{
// v <-- vertex with maximum degree in G'
System.Object v = SupportClass.CollectionsSupport.Max(sg.vertexSet(), comp);
// C <-- C U {v}
cover.Add(v);
// remove from G' every edge incident on v, and v itself
sg.removeVertex(v);
}
return(cover);
}
/// <summary> Finds a greedy approximation for a minimal vertex cover of a specified
/// graph. At each iteration, the algorithm picks the vertex with the
/// highest degree and adds it to the cover, until all edges are covered.
///
/// <p>
/// The algorithm works on undirected graphs, but can also work on directed
/// graphs when their edge-directions are ignored. To ignore edge
/// directions you can use {@link
/// org._3pq.jgrapht.GraphHelper#undirectedGraph(Graph)} or {@link
/// org._3pq.jgrapht.graph.AsUndirectedGraph}.
/// </p>
///
/// </summary>
/// <param name="g">the graph for which vertex cover approximation is to be found.
///
/// </param>
/// <returns> a set of vertices which is a vertex cover for the specified
/// graph.
/// </returns>
public virtual SupportClass.SetSupport findGreedyCover(UndirectedGraph g)
{
// C <-- {}
//UPGRADE_TODO: Class 'java.util.HashSet' was converted to 'SupportClass.HashSetSupport' which has a different behavior. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1073_javautilHashSet'"
SupportClass.SetSupport cover = new SupportClass.HashSetSupport();
// G' <-- G
UndirectedGraph sg = new UndirectedSubgraph(g, null, null);
// compare vertices in descending order of degree
VertexDegreeComparator comp = new VertexDegreeComparator(sg);
// while G' != {}
while (sg.edgeSet().Count > 0)
{
// v <-- vertex with maximum degree in G'
System.Object v = SupportClass.CollectionsSupport.Max(sg.vertexSet(), comp);
// C <-- C U {v}
cover.Add(v);
// remove from G' every edge incident on v, and v itself
sg.removeVertex(v);
}
return cover;
}
public UndirectedSubgraph(UndirectedGraph base_Renamed, SupportClass.SetSupport vertexSubset)
: base(base_Renamed, vertexSubset)
{ }
/// <summary> Creates a comparator for comparing the degrees of vertices in the
/// specified graph.
///
/// </summary>
/// <param name="g">graph with respect to which the degree is calculated.
/// </param>
/// <param name="ascendingOrder">true - compares in ascending order of degrees
/// (lowest first), false - compares in descending order of degrees
/// (highest first).
/// </param>
public VertexDegreeComparator(UndirectedGraph g, bool ascendingOrder)
{
m_graph = g;
m_ascendingOrder = ascendingOrder;
}
/// <summary> Creates a comparator for comparing the degrees of vertices in the
/// specified graph. The comparator compares in ascending order of degrees
/// (lowest first).
///
/// </summary>
/// <param name="g">graph with respect to which the degree is calculated.
/// </param>
public VertexDegreeComparator(UndirectedGraph g) : this(g, true)
{
}
/// <summary> Creates a new listenable undirected graph.
///
/// </summary>
/// <param name="base">the backing graph.
/// </param>
public ListenableUndirectedGraph(UndirectedGraph base_Renamed) : base(base_Renamed)
{
}
/// <summary> Creates a new unmodifiable undirected graph based on the specified
/// backing graph.
///
/// </summary>
/// <param name="g">the backing graph on which an unmodifiable graph is to be
/// created.
/// </param>
public UnmodifiableUndirectedGraph(UndirectedGraph g):base(g)
{
}
/// <summary> Creates a new unmodifiable undirected graph based on the specified
/// backing graph.
///
/// </summary>
/// <param name="g">the backing graph on which an unmodifiable graph is to be
/// created.
/// </param>
public UnmodifiableUndirectedGraph(UndirectedGraph g) : base(g)
{
}
public UndirectedSubgraph(UndirectedGraph base_Renamed, SupportClass.SetSupport vertexSubset)
: base(base_Renamed, vertexSubset)
{
}
/// <summary> Creates a comparator for comparing the degrees of vertices in the
/// specified graph.
///
/// </summary>
/// <param name="g">graph with respect to which the degree is calculated.
/// </param>
/// <param name="ascendingOrder">true - compares in ascending order of degrees
/// (lowest first), false - compares in descending order of degrees
/// (highest first).
/// </param>
public VertexDegreeComparator(UndirectedGraph g, bool ascendingOrder)
{
m_graph = g;
m_ascendingOrder = ascendingOrder;
}
/// <summary> Creates a comparator for comparing the degrees of vertices in the
/// specified graph. The comparator compares in ascending order of degrees
/// (lowest first).
///
/// </summary>
/// <param name="g">graph with respect to which the degree is calculated.
/// </param>
public VertexDegreeComparator(UndirectedGraph g):this(g, true)
{
}
