1 |
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2 | using System;
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3 | using System.Collections.Generic;
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4 | using HeuristicLab.Problems.RoutePlanning.Graph;
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5 | namespace HeuristicLab.Algorithms.GraphRouting {
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6 | public class AStarAlgorithm : IRouter {
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7 | private Graph graph;
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8 |
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9 | private Dictionary<long, float> distances;
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10 | private Dictionary<long, long> predecessors;
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11 | private List<float> closedList = new List<float>();
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12 | //private PriorityQueueOld<float, long> openList;
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13 | private PriorityQueue<float, long> openList;
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14 |
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15 | public AStarAlgorithm(Graph graph) {
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16 | this.graph = graph;
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17 | }
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18 |
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19 | #region IRouter Members
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20 |
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21 | public long[] Calculate(long sourceNodeId, long targetNodeId) {
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22 | distances = new Dictionary<long, float>();
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23 | predecessors = new Dictionary<long, long>();
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24 | closedList = new List<float>();
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25 | //openList = new PriorityQueueOld<float, long>();
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26 | openList = new PriorityQueue<float, long>(new MyComparer());
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27 |
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28 | long currentNode = sourceNodeId;
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29 |
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30 | //openList.Enqueue(currentNode, 0);
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31 | openList.Enqueue(0, currentNode);
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32 | distances.Add(currentNode, 0);
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33 |
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34 | while (openList.Count > 0) {
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35 | //currentNode = openList.Dequeue();
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36 | currentNode = openList.DequeueValue();
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37 | if (currentNode == targetNodeId) {
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38 | return ReconstructPath(currentNode).ToArray();
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39 | }
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40 |
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41 | Dictionary<long, float> currentNeighbors = graph.GetNeighbors(currentNode);
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42 | foreach (KeyValuePair<long, float> neighbor in currentNeighbors) {
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43 | if (closedList.Contains(neighbor.Key))
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44 | continue;
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45 |
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46 | float costsFromStart = GetDistance(currentNode) + neighbor.Value;
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47 |
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48 | if (openList.Contains(neighbor.Key) && costsFromStart > GetDistance(neighbor.Key))
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49 | continue;
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50 |
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51 | distances[neighbor.Key] = costsFromStart;
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52 | predecessors[neighbor.Key] = currentNode;
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53 |
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54 | float f = costsFromStart + graph.EstimatedCosts(neighbor.Key, targetNodeId);
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55 | if (openList.Contains(neighbor.Key)) {
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56 | openList.Remove(neighbor.Key);
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57 | }
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58 | //openList.Enqueue(neighbor.Key, f);
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59 | openList.Enqueue(f, neighbor.Key);
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60 | }
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61 | }
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62 | throw new Exception(string.Format("No route found from {0} to {1}", sourceNodeId, targetNodeId));
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63 | }
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64 |
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65 | #endregion
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66 |
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67 | private float GetDistance(long id) {
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68 | float d;
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69 | if (distances.TryGetValue(id, out d)) {
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70 | return d;
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71 | } else { return float.MaxValue; }
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72 |
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73 | }
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74 |
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75 | private List<long> ReconstructPath(long nodeId) {
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76 | List<long> route = new List<long>();
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77 | long current = nodeId;
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78 | long next;
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79 |
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80 | if (!predecessors.TryGetValue(current, out next)) {
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81 | return null;
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82 | }
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83 | route.Add(current);
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84 | while (predecessors.TryGetValue(current, out next)) {
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85 | current = predecessors[current];
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86 | route.Add(current);
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87 | }
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88 | route.Reverse();
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89 | return route;
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90 | }
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91 | }
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92 |
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93 | class MyComparer : IComparer<float> {
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94 | public int Compare(float item1, float item2) {
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95 | return item1 > item2 ? 1 : item1 < item2 ? -1 : 0;
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96 |
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97 | // inverted comparison
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98 | //return item1 < item2 ? 1 : item1 > item2 ? -1 : 0;
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99 | }
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100 | }
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101 | }
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