/**
* Makes the high level decision of which objects to visit. Uses a greedy best first search based
* on the sum of the distances between the ship, the object, and the master objective.
*
* @param space
* @param me
* @param finalObjective
* @return LinkedList of objects to visit, in order
*/
public static LinkedList<AbstractObject> getObjectsToVisit(
Toroidal2DPhysics space, Ship me, AbstractObject finalObjective) {
LinkedList<AbstractObject> objectsList = new LinkedList<AbstractObject>();
candidateObjects = new HashMap<AbstractObject, Double>();
AbstractObject nextObjective = finalObjective;
// set up the objects to search through
for (Beacon beacon : space.getBeacons()) {
candidateObjects.put(beacon, heuristicFunction(space, me, beacon, finalObjective));
}
for (Asteroid asteroid : space.getAsteroids()) {
if (!asteroid.isMineable()) continue;
candidateObjects.put(asteroid, heuristicFunction(space, me, asteroid, finalObjective));
}
// add the endpoint of our search so it will be the end of the list
objectsList.addFirst(finalObjective);
if (candidateObjects.containsKey(finalObjective)) candidateObjects.remove(finalObjective);
// keep adding new objects to list, using greedy best search until we are done
for (int i = MAX_DEPTH; i > 0; i--) {
nextObjective = findNextObject(space, me, nextObjective);
// check when to stop search
if (nextObjective == null
// don't go for objects outside of the radius from final object to me
|| space.findShortestDistance(finalObjective.getPosition(), nextObjective.getPosition())
> space.findShortestDistance(me.getPosition(), finalObjective.getPosition())) {
break;
}
objectsList.addFirst(nextObjective);
candidateObjects.remove(nextObjective);
}
return objectsList;
}
/**
* Calculating the sum of distances from a start object through a middle object to the end. Will
* be used as the heuristic for a greedy best search.
*
* @param space
* @param start
* @param middle
* @param end
* @return h value
*/
public static double heuristicFunction(
Toroidal2DPhysics space, AbstractObject start, AbstractObject middle, AbstractObject end) {
// heuristic function based on shortest detour
return space.findShortestDistance(start.getPosition(), middle.getPosition())
+ space.findShortestDistance(middle.getPosition(), end.getPosition());
}