Dijkstra's Algorithmus mit 'Must-Pass'-Knoten
Ich versuche, den Dijkstra-Algorithmus zu implementieren, der den kürzesten Weg zwischen dem Startknoten und dem Endknoten findet. Vor Erreichen des Endknotens müssen einige Zwischenknoten (mehr als einer) übergeben werden, z. B. 2 oder 3 müssen Knoten übergeben, die vor Erreichen des Endknotens übergeben werden müssen.
Wenn ich habe, muss man Knoten passieren die Lösung, die ich gefunden habe, ist, zwei verschiedene Pfade vom Muss-Übergabe-Knoten zum Ziel und vom Muss-Übergabe-Knoten zum Start-Knoten zu finden.
Ich habe keine Ahnung, wie ich einen solchen Algorithmus implementieren kann. Irgendwelche Vorschläge?
Vielen Dank.
List<Node> closestPathFromOrigin = null;
double maxD = Double.POSITIVE_INFINITY;
double _distance = 0;
int temp1 = 0;
List<Node> referencePath = new ArrayList<>();
boolean check = false;
Node startNode = null;
public List<Node> recursion(ArrayList<Node> points, ArrayList<Node> intermediatePoints) {
if (!check) {
System.out.println("--- DATA ---");
System.out.println("Intermediate points: " + intermediatePoints);
System.out.println("points: " + points.get(0).lat + " " + points.get(1).lat);
System.out.println("--Find the nearest intermediate point from the start point of driver--");
startNode = points.get(0);
System.out.println("Start point of driver: " + startNode.lat + " " + startNode.lon);
for (int i = 0; i < intermediatePoints.size(); i++) {
List<Node> _path = dijkstra(startNode, intermediatePoints.get(i));
_distance = 0;
for (int j = 0; j < _path.size() - 1; j++) {
_distance += calculateDistance(_path.get(j), _path.get(j + 1));
}
if (_distance < maxD) {
maxD = _distance;
closestPathFromOrigin = _path;
temp1 = i;
}
}
System.out.println("NearestPoint from driver's origin: " + intermediatePoints.get(temp1));
referencePath.addAll(closestPathFromOrigin);
startNode = intermediatePoints.get(temp1);
System.out.println("New StartNode: the nearestPoint from driver's origin: " + startNode.lat + " " + startNode.lon);
check = true;
intermediatePoints.remove(intermediatePoints.get(temp1));
System.out.println("New Intermediate points: " + intermediatePoints);
System.out.println("Intermediate points empty? No -> recursion, Yes -> stop");
if (!intermediatePoints.isEmpty()) {
System.out.println("Recursion!!! with new data of: intermediatePoints: " + intermediatePoints);
recursion(points, intermediatePoints);
} else {
System.out.println("Stop");
return referencePath;
}
} else {
System.out.println("Recursion: startNode: " + startNode.lat + " " + startNode.lon);
for (int i = 0; i < intermediatePoints.size(); i++) {
if (intermediatePoints.size() > 1) {
System.out.println("From the new start point to the next nearest intermediate points if more than one points");
List<Node> _path = dijkstra(startNode, intermediatePoints.get(i));
_distance = 0;
for (int j = 0; j < _path.size() - 1; j++) {
_distance += calculateDistance(_path.get(j), _path.get(j + 1));
}
if (_distance < maxD) {
maxD = _distance;
closestPathFromOrigin = _path;
temp1 = i;
}
referencePath.addAll(closestPathFromOrigin);
startNode = intermediatePoints.get(temp1);
check = true;
intermediatePoints.remove(intermediatePoints.get(temp1));
if (!intermediatePoints.isEmpty()) {
recursion(points, intermediatePoints);
} else {
return referencePath;
}
} else {
System.out.println("From the new start point to the next nearest intermediate points if just one point");
List<Node> _path = dijkstra(startNode, intermediatePoints.get(i));
//Collections.reverse(_path);
referencePath.addAll(_path);
}
if (i == intermediatePoints.size() - 1) {
System.out.println("Last Entry in intermediate points - find path to destination: " + points.get(1).lat + " " + intermediatePoints.get(i));
//List<Node> _path1 = dijkstra(points.get(1), intermediatePoints.get(i));
List<Node> _path1 = dijkstra(intermediatePoints.get(i), points.get(1));
Collections.reverse(_path1);
referencePath.addAll(_path1);
// referencePath.addAll(_path2);
}
}
}
return referencePath;
}