public UndirectedGraph FindMinimumSpanningTree()
{
var tree = new UndirectedGraph();
var priorityQueue = new CustomPriotiryQueueForPrim();
var startNode = Vertices.Values.First();
startNode.Edges.ForEach(edge => priorityQueue.Push(edge));
tree.AddNode(startNode.Label);
while (tree.Vertices.Count < Vertices.Count)
{
var minimumWeightEdge = priorityQueue.Pop();
var nextNode = minimumWeightEdge.To;
if (tree.ContainsNode(nextNode.Label))
{
continue;
}
tree.AddNode(nextNode.Label);
tree.AddEdge(minimumWeightEdge.From.Label, nextNode.Label, minimumWeightEdge.Weight);
nextNode.Edges.ForEach(edge =>
{
if (!tree.ContainsNode(edge.To.Label))
{
priorityQueue.Push(edge);
}
});
}
return(tree);
}
/// <summary>
/// Recursive Implementation For Prim
/// </summary>
/// <param name="node"></param>
/// <param name="spanningTree"></param>
/// <param name="visited"></param>
/// <param name="priotiryQueueForPrim"></param>
/// <param name="path"></param>
private void FindMinimumSpanningTree(Node node, UndirectedGraph spanningTree, HashSet <Node> visited, CustomPriotiryQueueForPrim priotiryQueueForPrim, Path path)
{
if (!visited.Contains(node))
{
visited.Add(node);
path.AddNode(node.Label);
foreach (var edge in node.Edges)
{
priotiryQueueForPrim.Push(edge);
}
Edge edgeToVisit = null;
while (edgeToVisit == null && priotiryQueueForPrim.Count() > 0)
{
var minimumPriorityEdge = priotiryQueueForPrim.Pop();
if (!visited.Contains(minimumPriorityEdge.To))
{
edgeToVisit = minimumPriorityEdge;
spanningTree.AddNode(edgeToVisit.From.Label);
spanningTree.AddNode(edgeToVisit.To.Label);
spanningTree.AddEdge(edgeToVisit.From.Label, edgeToVisit.To.Label, edgeToVisit.Weight);
}
}
if (edgeToVisit != null)
{
FindMinimumSpanningTree(edgeToVisit.To, spanningTree, visited, priotiryQueueForPrim, path);
}
}
}
