Exemple #1
0
        static void Main(string[] args)
        {
            var graph = new CustomWeightedGraph();

            graph.AddNode("A");
            graph.AddNode("B");
            graph.AddNode("C");
            graph.AddNode("D");

            graph.AddEdge("A", "B", 3);
            graph.AddEdge("B", "C", 2);
            graph.AddEdge("B", "D", 4);
            graph.AddEdge("A", "C", 1);
            graph.AddEdge("C", "D", 5);
            graph.Print();

            var from = "A";
            var to   = "D";

            Console.WriteLine($"Shortest Distance {from}->{to} : {graph.GetShortestDistance(from, to)}");
            Console.WriteLine($"Shortest Path {from}->{to}");
            graph.GetShortestPath(from, to).Print();

            Console.WriteLine($"Graph has cycle? : {graph.HasCycle()}");

            Console.WriteLine("Creating Minimum Span Tree using Prim's Algorithm");
            var minimumSpanTree = graph.MinimumSpanTree();

            minimumSpanTree.Print();
        }
        public CustomWeightedGraph MinimumSpanTree()
        {
            // Prim's Algorithm
            var minSpanTree        = new CustomWeightedGraph();
            var totalNodes         = GetTotalNodes();
            var nodes              = new HashSet <Node>();
            var edgesPriorityQueue = new C5.IntervalHeap <Edge>(new EdgeComp());

            if (itemsMap.Count == 0)
            {
                return(minSpanTree);            // Error Handling
            }
            var node = itemsMap.Values.First(); // Randomly pick the first node to add to Minimum Span Tree

            nodes.Add(node);
            minSpanTree.AddNode(node.label);
            edgesPriorityQueue.AddAll(node.GetEdges());

            while (nodes.Count < totalNodes)
            {
                var minEdge = edgesPriorityQueue.DeleteMax();

                if (minSpanTree.ContainNode(minEdge.to.label) && minSpanTree.ContainNode(minEdge.from.label))
                {
                    continue;
                }

                node = minEdge.to;
                nodes.Add(node);

                minSpanTree.AddNode(node.label);
                minSpanTree.AddEdge(minEdge.from.label, minEdge.to.label, minEdge.weight);
                edgesPriorityQueue.AddAll(node.GetEdges().Where(e => !minSpanTree.ContainNode(e.to.label)));
            }
            return(minSpanTree);
        }