92 lines
2.9 KiB
Java
92 lines
2.9 KiB
Java
import java.io.*;
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public class SierpinskiSquareCurve {
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public static void main(final String[] args) {
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try (Writer writer = new BufferedWriter(new FileWriter("sierpinski_square.svg"))) {
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SierpinskiSquareCurve s = new SierpinskiSquareCurve(writer);
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int size = 635, length = 5;
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s.currentAngle = 0;
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s.currentX = (size - length)/2;
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s.currentY = length;
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s.lineLength = length;
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s.begin(size);
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s.execute(rewrite(5));
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s.end();
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} catch (final Exception ex) {
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ex.printStackTrace();
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}
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}
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private SierpinskiSquareCurve(final Writer writer) {
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this.writer = writer;
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}
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private void begin(final int size) throws IOException {
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write("<svg xmlns='http://www.w3.org/2000/svg' width='%d' height='%d'>\n", size, size);
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write("<rect width='100%%' height='100%%' fill='white'/>\n");
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write("<path stroke-width='1' stroke='black' fill='none' d='");
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}
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private void end() throws IOException {
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write("'/>\n</svg>\n");
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}
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private void execute(final String s) throws IOException {
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write("M%g,%g\n", currentX, currentY);
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for (int i = 0, n = s.length(); i < n; ++i) {
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switch (s.charAt(i)) {
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case 'F':
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line(lineLength);
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break;
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case '+':
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turn(ANGLE);
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break;
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case '-':
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turn(-ANGLE);
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break;
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}
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}
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}
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private void line(final double length) throws IOException {
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final double theta = (Math.PI * currentAngle) / 180.0;
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currentX += length * Math.cos(theta);
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currentY += length * Math.sin(theta);
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write("L%g,%g\n", currentX, currentY);
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}
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private void turn(final int angle) {
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currentAngle = (currentAngle + angle) % 360;
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}
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private void write(final String format, final Object... args) throws IOException {
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writer.write(String.format(format, args));
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}
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private static String rewrite(final int order) {
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String s = AXIOM;
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for (int i = 0; i < order; ++i) {
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final StringBuilder sb = new StringBuilder();
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for (int j = 0, n = s.length(); j < n; ++j) {
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final char ch = s.charAt(j);
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if (ch == 'X')
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sb.append(PRODUCTION);
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else
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sb.append(ch);
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}
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s = sb.toString();
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}
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return s;
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}
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private final Writer writer;
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private double lineLength;
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private double currentX;
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private double currentY;
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private int currentAngle;
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private static final String AXIOM = "F+XF+F+XF";
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private static final String PRODUCTION = "XF-F+F-XF+F+XF-F+F-X";
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private static final int ANGLE = 90;
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}
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