コード例 #1
0
ファイル: AStarSearch.cs プロジェクト: RainsSoft/UJad-AI-VFS
        /// <summary>
        /// Searches in a graph
        /// </summary>
        /// <returns>The state of the search</returns>
        public override SearchState Search()
        {
            int      closestNode;
            List <K> edges;
            double   hCost, gCost;

            while (queue.Count != 0)
            {
                //Dequeue the first node (the one with the lower cost) and add it to the shortest path tree
                closestNode = queue.Dequeue();
                shortestPathTree[closestNode] = frontier[closestNode];

                //If it´s the target, return
                if (closestNode == target)
                {
                    found = SearchState.CompletedAndFound;
                    return(found);
                }

                //Get all edges that start from the current node
                edges = graph.GetEdgesFromNode(closestNode);
                for (int i = 0; i < edges.Count; i++)
                {
                    //Calculate the estimated cost to reach the target from the next node
                    hCost = heuristic(graph, target, edges[i].End);

                    //Calculate the cost to reach the next node with the current one and the edge
                    gCost = gCosts[closestNode] + edges[i].Cost;

                    //If the node wasn´t in the frontier, add it
                    if (frontier[edges[i].End] == null)
                    {
                        fCosts[edges[i].End] = gCost + hCost;
                        gCosts[edges[i].End] = gCost;

                        queue.Enqueue(edges[i].End);
                        frontier[edges[i].End] = edges[i];
                    }

                    else                     //If it was, see if the new way of reaching the node is shorter or not. If it´s shorter, update the cost to reach it
                    {
                        if ((gCost < gCosts[edges[i].End]) && (shortestPathTree[edges[i].End] == null))
                        {
                            fCosts[edges[i].End] = gCost + hCost;
                            gCosts[edges[i].End] = gCost;

                            queue.ChangePriority(edges[i].End);
                            frontier[edges[i].End] = edges[i];
                        }
                    }
                }
            }

            found = SearchState.CompletedAndNotFound;
            return(found);
        }