public class ClosestPair {
  public final static double INF = java.lang.Double.POSITIVE_INFINITY;

  public static PointPair closestPair(XYPoint[] points){
    XYPoint pointsByX [] = new XYPoint [points.length];
    XYPoint pointsByY [] = new XYPoint [points.length];
	for (int j = 0; j < points.length; j++)
	  {
	    pointsByX[j] = points[j];
	    pointsByY[j] = points[j];
	  }
	
	// Ensure sorting precondition for divide-and-conquer algorithm.
	XComparator xcomp = new XComparator();
	YComparator ycomp = new YComparator();
	Sort.msort(pointsByX, xcomp); // sort by x-coord
	Sort.msort(pointsByY, ycomp); // sort by y-coord
  	return findClosestPair(pointsByX, pointsByY);
  }

  static PointPair findClosestPair(XYPoint[] ptsByX, XYPoint[] ptsByY){
    //  This is the recursive procedure -- you take it from here
    //  Just so this will compile without modification, right now it will
    //  return the first two points in ptsByX
    return new PointPair(ptsByX[0],ptsByX[1]);
  }
}