/// <summary>
        /// Execute Dijkstra's algorithm
        /// </summary>
        /// <param name="start"></param>
        /// <returns></returns>
        private static Dictionary<Node, DijkstraEntry> ExecuteDijkstrasAlgorithm(Node start)
        {
            Dictionary<Node, DijkstraEntry> result = new Dictionary<Node, DijkstraEntry>();
            result[start] = new DijkstraEntry { Via = start, Cost = 0f, Known = true };

            Node currentNode = start;

            while (currentNode != null)
            {
                // The best path to get to the current node is definitely known
                result[currentNode].Known = true;

                foreach (Node neighbor in currentNode.Neighbors)
                {
                    // Check if it's a Node we've already analyzed
                    if (result.ContainsKey(neighbor) && result[neighbor].Known)
                        continue;

                    // Calculate distance from the current (known) Node
                    float distanceFromCurrentNode = (currentNode.Position - neighbor.Position).LengthSquared();

                    if (result.ContainsKey(neighbor))
                    {
                        DijkstraEntry existingEntry = result[neighbor];

                        // Check if a better path is available
                        if (result[currentNode].Cost + distanceFromCurrentNode < existingEntry.Cost)
                        {
                            existingEntry.Via = currentNode;
                            existingEntry.Cost = result[currentNode].Cost + distanceFromCurrentNode;
                        }
                    }
                    else
                    {
                        result[neighbor] = new DijkstraEntry
                        {
                            Via = currentNode,
                            Cost = result[currentNode].Cost + distanceFromCurrentNode,
                            Known = false
                        };
                    }
                }

                // Search for the next node to analyze
                currentNode = null;

                // In the set of unknown Nodes, find the one that has the least "cost" and set Known = true
                KeyValuePair<Node, DijkstraEntry> nextKnownNode = result
                    .Where(n => !n.Value.Known)
                    .OrderBy(n => n.Value.Cost)
                    .FirstOrDefault();

                if (nextKnownNode.Key != null)
                    currentNode = nextKnownNode.Key;
            }

            return result;
        }
        public static Dictionary<Node, Node> BuildShortestPathDictionary(Node node)
        {
            // Run Dijkstra's algorithm
            Dictionary<Node, DijkstraEntry> dijkstrasAlgorithmResult = ExecuteDijkstrasAlgorithm(node);

            // Construct result
            Dictionary<Node, Node> result = new Dictionary<Node, Node>();

            foreach (Node key in dijkstrasAlgorithmResult.Keys)
            {
                result.Add(key, dijkstrasAlgorithmResult[key].Via);
            }

            return result;
        }
Example #3
0
 /// <summary>
 /// Gets the best Node to take on the way to the goal Node
 /// </summary>
 /// <param name="goal"></param>
 /// <returns></returns>
 public Node GetShortestPathNode(Node goal)
 {
     return this.ShortestPathDictionary[goal];
 }
Example #4
0
        /// <summary>
        /// Returns the best node to travserse next in order to eventually reach the given goal Node
        /// </summary>
        /// <param name="goalNode"></param>
        /// <returns></returns>
        public Node GetNextNode(Node goalNode)
        {
            if (goalNode == this)
                return null;

            // The shortest path information is assumed to be in the ShortestPathDictionary
            Node result = this.ShortestPathDictionary[goalNode];

            return result;
        }
Example #5
0
 /// <summary>
 /// Add edge
 /// </summary>
 /// <param name="node1"></param>
 /// <param name="node2"></param>
 public void AddEdge(Node node1, Node node2)
 {
     node1.Neighbors.Add(node2);
     node2.Neighbors.Add(node1);
 }
Example #6
0
 public DijkstraEntry()
 {
     this.Known = false;
     this.Via = null;
     this.Cost = float.MaxValue;
 }