public static void main(String[] args) {
Point[] points = new Point[500];
for (int i = 0; i < points.length; i++) {
points[i] = new Point((int) (Math.random() * 1000000), (int) (Math.random() * 1000000));
}
Pair pair = Pair.getClosestPair(points);
System.out.println(pair.getP1());
System.out.println(pair.getP2());
System.out.println(pair.getDistance());
}
public static Pair distance(
Point[] pointsOrderedOnX, int low, int high, Point[] pointsOrderedOnY) {
if (low >= high) {
return null;
} else if (low + 1 == high) {
return new Pair(pointsOrderedOnX[low], pointsOrderedOnX[high]);
}
int halfSize = (low + high) / 2;
Pair p1 = distance(pointsOrderedOnX, low, halfSize, pointsOrderedOnY);
Pair p2 = distance(pointsOrderedOnX, halfSize + 1, high, pointsOrderedOnY);
double distance = 0;
Pair p = null;
if (p1 == null && p2 == null) {
distance = Double.MAX_VALUE;
} else if (p1 == null) {
distance = p2.getDistance();
p = p2;
} else if (p2 == null) {
distance = p1.getDistance();
p = p1;
} else {
distance = Math.min(p1.getDistance(), p2.getDistance());
p = ((p1.getDistance() <= p2.getDistance()) ? p1 : p2);
}
ArrayList<Point> stripL = new ArrayList<Point>();
ArrayList<Point> stripR = new ArrayList<Point>();
for (int i = 0; i < pointsOrderedOnY.length; i++) {
if ((pointsOrderedOnY[i].getX() <= pointsOrderedOnX[halfSize].getX())
&& (pointsOrderedOnY[i].getX() >= pointsOrderedOnX[halfSize].getX() - distance)) {
stripL.add(pointsOrderedOnY[i]);
} else {
stripR.add(pointsOrderedOnY[i]);
}
}
double d3 = distance;
int r = 0;
for (int i = 0; i < stripL.size(); i++) {
while (r < stripR.size() && stripL.get(i).getY() > stripR.get(r).getY() + distance) {
r++;
}
int r1 = r;
while (r1 < stripR.size() && stripR.get(r1).getY() <= stripL.get(i).getY() + distance) {
if (d3 > distance(stripL.get(i), stripR.get(r1))) {
d3 = distance(stripL.get(i), stripR.get(r1));
p.p1 = stripL.get(i);
p.p2 = stripR.get(r1);
}
r1++;
}
}
return p;
}
