public class Turtle { private double x, y; private double angle; public Turtle(d
ID: 3545962 • Letter: P
Question
public class Turtle {
private double x, y;
private double angle;
public Turtle(double x0, double y0, double a0) {
x = x0;
y = y0;
angle = a0;
}
public void turnLeft(double delta) {
angle += delta;
}
public void goForward(double step) {
double oldx = x;
double oldy = y;
x += step * Math.cos(Math.toRadians(angle));
y += step * Math.sin(Math.toRadians(angle));
StdDraw.line(oldx, oldy, x, y);
}
public static void main(String[] args)
{
int N = Integer.parseInt(args[0]);
double angle = 360.0/N
double step = Math.sin(Math.toRadians(angle/2));
Turtle turtle = new turtle(.5, .0, angle/2);
for (int i = 0; i < N; i++)
{
turtle.goforward(step);
turtle.turnleft(angle);
}
}
}
Modify the test client in the above program to produce stars with N points for odd N
Explanation / Answer
import java.awt.Color;
public class Turtle {
private double x, y; // turtle is at (x, y)
private double angle; // facing this many degrees counterclockwise from the x-axis
// start at (x0, y0), facing a0 degrees counterclockwise from the x-axis
public Turtle(double x0, double y0, double a0) {
x = x0;
y = y0;
angle = a0;
}
// rotate orientation delta degrees counterclockwise
public void turnLeft(double delta) {
angle += delta;
}
// move forward the given amount, with the pen down
public void goForward(double step) {
double oldx = x;
double oldy = y;
x += step * Math.cos(Math.toRadians(angle));
y += step * Math.sin(Math.toRadians(angle));
StdDraw.line(oldx, oldy, x, y);
}
// pause t milliseconds
public void pause(int t) {
StdDraw.show(t);
}
public void setPenColor(Color color) {
StdDraw.setPenColor(color);
}
public void setPenRadius(double radius) {
StdDraw.setPenRadius(radius);
}
public void setCanvasSize(int width, int height) {
StdDraw.setCanvasSize(width, height);
}
public void setXscale(double min, double max) {
StdDraw.setXscale(min, max);
}
public void setYscale(double min, double max) {
StdDraw.setYscale(min, max);
}
// sample client for testing
public static void main(String[] args) {
double x0 = 0.5;
double y0 = 0.0;
double a0 = 60.0;
double step = Math.sqrt(3)/2;
Turtle turtle = new Turtle(x0, y0, a0);
turtle.goForward(step);
turtle.turnLeft(120.0);
turtle.goForward(step);
turtle.turnLeft(120.0);
turtle.goForward(step);
turtle.turnLeft(120.0);
}
}
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