public LinkedList <Vertex> GetSortedMergedVertex(ContractibleEdge pCe)
{
LinkedList <Vertex> sortedMergedList = new LinkedList <Vertex>();
LinkedListNode <Vertex> headCurrNode = pCe.Head.First, tailCurrNode = pCe.Tail.First;
for (int i = 0; i < pCe.Head.Count + pCe.Tail.Count; i++)
{
if (headCurrNode != null && tailCurrNode != null)
{
if (headCurrNode.Value.Label <= tailCurrNode.Value.Label)
{
sortedMergedList.AddLast(new LinkedListNode <Vertex>(headCurrNode.Value));
headCurrNode = headCurrNode.Next;
}
else
{
sortedMergedList.AddLast(new LinkedListNode <Vertex>(tailCurrNode.Value));
tailCurrNode = tailCurrNode.Next;
}
}
if (headCurrNode == null && tailCurrNode != null)
{
sortedMergedList.AddLast(new LinkedListNode <Vertex>(tailCurrNode.Value));
tailCurrNode = tailCurrNode.Next;
}
if (tailCurrNode == null && headCurrNode != null)
{
sortedMergedList.AddLast(new LinkedListNode <Vertex>(headCurrNode.Value));
headCurrNode = headCurrNode.Next;
}
}
return(sortedMergedList);
}
public LinkedList <Edge> GetCrossingEdgesForMinCut()
{
int minCutCrossingEdgeCount = -1;
LinkedList <Edge> minCutCrossingEdges = null;
long noOfTrials = Vertices.Count * Vertices.Count; //n^2
for (long trialCount = 0; trialCount < noOfTrials; trialCount++)
{
ContractibleGraph cGraph = new ContractibleGraph(this);
int unMergedVertices = Vertices.Count;
while (unMergedVertices > 2)
{
ContractibleEdge ce = cGraph.GetEdgeToContractUniformlyAtRandom();
cGraph.ContractEdgeAndDeleteSelfLoops(ce);
unMergedVertices--;
}
if (minCutCrossingEdgeCount == -1 || cGraph.ContractibleEdges.Count < minCutCrossingEdgeCount)
{
minCutCrossingEdgeCount = cGraph.ContractibleEdges.Count;
minCutCrossingEdges = new LinkedList <Edge>();
for (int i = 0; i < minCutCrossingEdgeCount; i++)
{
minCutCrossingEdges.AddLast(cGraph.ContractibleEdges.First().OriginalEdge);
cGraph.ContractibleEdges.RemoveFirst();
}
}
}
return(minCutCrossingEdges);
}
private LinkedList <ContractibleEdge> GetContractibleEdgesForGraph()
{
LinkedList <ContractibleEdge> result = new LinkedList <ContractibleEdge>();
foreach (Edge e in OriginalGraph.Edges)
{
ContractibleEdge cEdge = new ContractibleEdge();
cEdge.OriginalEdge = e;
cEdge.Head = new LinkedList <Vertex>();
cEdge.Head.AddLast(e.Head);
cEdge.Tail = new LinkedList <Vertex>();
cEdge.Tail.AddLast(e.Tail);
result.AddLast(cEdge);
}
return(result);
}
public void ContractEdgeAndDeleteSelfLoops(ContractibleEdge pCe)
{
//Sorted for faster comparison later while replacing component vertices with merged ones
LinkedList <Vertex> sortedMergedVertex = GetSortedMergedVertex(pCe);
LinkedListNode <ContractibleEdge> currNode = ContractibleEdges.First;
while (currNode != null)
{
LinkedListNode <ContractibleEdge> nextNode = currNode.Next;
if (currNode.Value == pCe)
{
ContractibleEdges.Remove(currNode);
currNode = nextNode;
continue;
}
//Replace component vertices at all places with merged vertex
if (AreSameSortedMergedVertex(pCe.Head, currNode.Value.Head) ||
AreSameSortedMergedVertex(pCe.Tail, currNode.Value.Head))
{
currNode.Value.Head = sortedMergedVertex;
}
if (AreSameSortedMergedVertex(pCe.Tail, currNode.Value.Tail) ||
AreSameSortedMergedVertex(pCe.Head, currNode.Value.Tail))
{
currNode.Value.Tail = sortedMergedVertex;
}
//Delete Self Loops
if (AreSameSortedMergedVertex(currNode.Value.Head, currNode.Value.Tail))
{
ContractibleEdges.Remove(currNode);
}
currNode = nextNode;
}
}
