/**
* Finds and returns the closest point containing a city to the given point. Does not include
* provided point as a possible city location.
*
* <p>If there are no cities, null is returned.
*
* @param point
* @return
*/
public Coord closestCity(Coord point) {
double dist = 999999999, newdist;
Coord closest = null;
for (Coord c : cities) {
if (c.equals(point)) {
continue; // skip the one being tested for
}
newdist = Math.pow(point.x - c.x, 2) + Math.pow(point.y - c.y, 2);
if (newdist < dist) {
dist = newdist;
closest = c;
}
}
return closest;
}
/**
* Finds an A* path to the target from the start. If no path is possible, returns null.
*
* @param startx the x coordinate of the start location
* @param starty the y coordinate of the start location
* @param targetx the x coordinate of the target location
* @param targety the y coordinate of the target location
* @return the shortest path, or null
*/
public Queue<Coord> path(int startx, int starty, int targetx, int targety) {
start = Coord.get(startx, starty);
target = Coord.get(targetx, targety);
open.clear();
finished = new boolean[width][height];
parent = new Coord[width][height];
Direction[] dirs;
switch (type) {
case MANHATTAN:
dirs = Direction.CARDINALS;
break;
case CHEBYSHEV:
case EUCLIDEAN:
case DIJKSTRA:
default:
dirs = Direction.OUTWARDS;
break;
}
Coord p = start;
open.add(p);
while (!p.equals(target)) {
finished[p.x][p.y] = true;
open.remove(p);
for (Direction dir : dirs) {
int x = p.x + dir.deltaX;
if (x < 0 || x >= width) {
continue; // out of bounds so skip ahead
}
int y = p.y + dir.deltaY;
if (y < 0 || y >= height) {
continue; // out of bounds so skip ahead
}
if (!finished[x][y]) {
Coord test = Coord.get(x, y);
if (open.contains(test)) {
double parentG = g(parent[x][y].x, parent[x][y].y);
if (parentG < 0) {
continue; // not a valid point so skip ahead
}
double g = g(p.x, p.y);
if (g < 0) {
continue; // not a valid point so skip ahead
}
if (parent[x][y] == null || parentG > g) {
parent[x][y] = p;
}
} else {
open.add(test);
parent[x][y] = p;
}
}
}
p = smallestF();
if (p == null) {
return null; // no path possible
}
}
Deque<Coord> deq = new ArrayDeque<>();
while (!p.equals(start)) {
deq.offerFirst(p);
p = parent[p.x][p.y];
}
return deq;
}