《算法》1.2-习题解答

1.2.1

package chapter1;

import edu.princeton.cs.algs4.Point2D;
import edu.princeton.cs.algs4.StdDraw;
import edu.princeton.cs.algs4.StdRandom;

public class prac1_2_Point2D {
    public static void main(String[] args) {
        int N = Integer.parseInt(args[0]);
        StdDraw.setCanvasSize(800, 800);
        StdDraw.setXscale(0, 50);
        StdDraw.setYscale(0, 50);
        StdDraw.setPenRadius(.005);
        Point2D[] points = new Point2D[N];
        for (int i = 0; i < N; i++) {
            int x = StdRandom.uniform(50);
            int y = StdRandom.uniform(50);
            points[i] = new Point2D(x, y);
            points[i].draw();
        }
        double min = Double.POSITIVE_INFINITY;
        int p1 = 0, p2 = 0;
        for (int i = 0; i < N; i++) {
            for (int j = i + 1; j < N; j++) {
                double dis = points[i].distanceTo(points[j]);
                if (dis < min) {
                    min = dis;
                    p1 = i;
                    p2 = j;
                }
            }
        }
        StdDraw.setPenColor(StdDraw.BLUE);
        StdDraw.line(points[p1].x(), points[p1].y(), points[p2].x(), points[p2].y());
    }
}

1.2.2

package chapter1;

import edu.princeton.cs.algs4.Interval1D;

public class prac1_2_Interval1D {
    public static void main(String[] args) {
        Interval1D[] intervals = new Interval1D[4];
        intervals[0] = new Interval1D(15.0, 33.0);
        intervals[1] = new Interval1D(45.0, 60.0);
        intervals[2] = new Interval1D(20.0, 70.0);
        intervals[3] = new Interval1D(46.0, 55.0);
        for (int i = 0; i < intervals.length; i++) {
            for (int j = i + 1; j < intervals.length; j++) {
                if (intervals[i].intersects(intervals[j]) == true) {
                    System.out.printf("%.1f %.1f, %.1f %.1f\n", intervals[i].min(), intervals[i].max(),
                            intervals[j].min(), intervals[j].max());
                }
            }
        }
    }
}