public static Graph <T> CreateMinimumSpanningTreeFor <T>(Graph <T> graph) where T : class, IEquatable <T>
{
var visitedVertices = new HashSet <Vertex <T> >();
if (!graph.IsConnected || graph.IsDirected)
{
throw new InvalidOperationException("The graph doesn't meet the characteristics to be used with Prim algorythm.");
}
var minBinaryHeap = new MinBinaryHeap <T>(graph, graph.Vertices.Values.First());
while (!minBinaryHeap.IsEmpty())
{
var vertexOnAnalysis = minBinaryHeap.ExtractFromTop();
foreach (var edge in vertexOnAnalysis.AdjacentEdges.Where(x => !visitedVertices.Contains(x.To) && !visitedVertices.Contains(x.From)))
{
var other = edge.To == vertexOnAnalysis ? edge.From : edge.To;
if (minBinaryHeap.Contains(other, out float?value))
{
if (value.Value > edge.Weight.Value)
{
minBinaryHeap.ReplaceValue(other, edge.Weight.Value, edge);
}
}
}
visitedVertices.Add(vertexOnAnalysis);
}
return(BuildNewGraph(graph, minBinaryHeap));
}
private void CheckNeighbour(PathNode currentNode, PathNode neighbour, PathNode endNode)
{
int newDistanceCost = currentNode.GCost + currentNode.GetDistanceCost(neighbour);
if (newDistanceCost < neighbour.GCost || !_openSet.Contains(neighbour))
{
neighbour.UpdateNode(newDistanceCost, neighbour.GetDistanceCost(endNode), currentNode);
if (!_openSet.Contains(neighbour))
{
_openSet.Add(neighbour);
}
else
{
_openSet.Heapify(neighbour);
}
}
}