public static List <Edge <T> > GetMSTUsingPrims <T>(this Graph <T> g) { BinaryMinHeap <Vertex <T> > minHeap = new BinaryMinHeap <Vertex <T> >(); //Set all nodes in hash map to infinity Dictionary <Vertex <T>, Edge <T> > vertexToEdgeMap = new Dictionary <Vertex <T>, Edge <T> >(); //Final result var result = new List <Edge <T> >(); //insert all vertices with infinite value initially. foreach (var v in g.AllVertex.Values) { minHeap.AddNode(Int32.MaxValue, v); } //Start from Random Vertex and decrease min heap to 0 Vertex <T> startVertex = g.AllVertex.FirstOrDefault().Value; minHeap.Decrease(startVertex, 0); //iterate till heap + map has elements in it while (!minHeap.IsEmpty()) { //Extract the min vertex from heap var minVertex = minHeap.extractMin().Data; //get the corresponding edge for this vertex if present and add it to final result. //This edge wont be present for first vertex. Edge <T> spanningTreeEdge = vertexToEdgeMap.ContainsKey(minVertex) ? vertexToEdgeMap[minVertex] : null; if (spanningTreeEdge != null) { result.Add(spanningTreeEdge); } //Iterate through all the edges for the current minVertex foreach (var edge in minVertex.GetAdjEdges()) { Vertex <T> otherVertex = GetVertexForEdge(minVertex, edge); //Check if the other vertex already exists in the map and weight attached is greater than weight of the edge. If yes, replace if (minHeap.ContainsData(otherVertex) && minHeap.GetWeight(otherVertex) > edge.Weight) { minHeap.Decrease(otherVertex, edge.Weight); if (vertexToEdgeMap.ContainsKey(otherVertex)) { vertexToEdgeMap[otherVertex] = edge; } else { vertexToEdgeMap.Add(otherVertex, edge); } } } } return(result); }
public static Dictionary <Vertex <T>, Int32> DjkstrasAlgo <T>(this Graph <T> g, Vertex <T> source, Dictionary <Vertex <T>, Vertex <T> > pathMap) { BinaryMinHeap <Vertex <T> > minHeap = new BinaryMinHeap <Vertex <T> >(); Dictionary <Vertex <T>, Int32> distanceMap = new Dictionary <Vertex <T>, int>(); //Dictionary<Vertex<T>, Vertex<T>> pathMap = new Dictionary<Vertex<T>, Vertex<T>>(); //Set all weights to infinity in minHeap foreach (var v in g.AllVertex.Values) { minHeap.AddNode(Int32.MaxValue, v); } //Decrease the weight of source to 0 minHeap.Decrease(source, 0); pathMap.Add(source, null); while (!minHeap.IsEmpty()) { //Extract the min int weight = minHeap.MinNode().Weight; var currentVertex = minHeap.extractMin().Data; distanceMap.AddOrUpdateDictionary(currentVertex, weight); foreach (var edge in currentVertex.GetAdjEdges()) { var otherVertex = GetVertexForEdge(currentVertex, edge); if (minHeap.ContainsData(otherVertex) && minHeap.GetWeight(otherVertex) > (edge.Weight + weight)) { minHeap.Decrease(otherVertex, (edge.Weight + weight)); pathMap.AddOrUpdateDictionary(otherVertex, currentVertex); } } } return(distanceMap); }