Point.java

import java.util.Comparator;

public class Point implements Comparable<Point> {

    // compare points by slope
    public final Comparator<Point> SLOPE_ORDER = new SlopeComparator();       // YOUR DEFINITION HERE

    private final int x;                              // x coordinate
    private final int y;                              // y coordinate

    // create the point (x, y)
    public Point(int x, int y) {
        /* DO NOT MODIFY */
        this.x = x;
        this.y = y;
    }

    // plot this point to standard drawing
    public void draw() {
        /* DO NOT MODIFY */
        StdDraw.point(x, y);
    }

    // draw line between this point and that point to standard drawing
    public void drawTo(Point that) {
        /* DO NOT MODIFY */
        StdDraw.line(this.x, this.y, that.x, that.y);
    }

    // slope between this point and that point
    public double slopeTo(Point that) {
        /*(y1 − y0)/(x1 − x0)*/
        if (this.x == that.x) 
            return this.y == that.y ? Double.NEGATIVE_INFINITY : Double.POSITIVE_INFINITY;
        if (this.y == that.y) 
            return 0;
        return (this.y - that.y)/((double) this.x - that.x);
    }

    // is this point lexicographically smaller than that one?
    // comparing y-coordinates and breaking ties by x-coordinates
    public int compareTo(Point that) {
        if (this.y > that.y) return +1;
        if (this.y < that.y) return -1;
        if (this.x > that.x) return +1;
        if (this.x < that.x) return -1;
        return 0;
    }

    // return string representation of this point
    public String toString() {
        /* DO NOT MODIFY */
        return "(" + x + ", " + y + ")";
    }

    private class SlopeComparator implements Comparator<Point> {

        public int compare(Point o1, Point o2) {
            return Double.compare(slopeTo(o1),slopeTo(o2));
        }
    }
}