Vortex.java

import java.util.Iterator;

/**
 * Created by orekyuuPC on 14/04/26.
 */
public class Vortex {

	private enum Dir {
		CENTER(0, 0), //
		UP(0, -1), //
		DOWN(0, 1), //
		LEFT(-1, 0), //
		RIGHT(1, 0), //
		UP_LEFT(UP.getY(), LEFT.getX()), //
		UP_RIGHT(UP.getY(), RIGHT.getX()), //
		DOWN_LEFT(DOWN.getY(), LEFT.getX()), //
		DOWN_RIGHT(DOWN.getY(), RIGHT.getX()), //
		;
		final int x;

		final int y;

		private Dir(int x, int y) {
			this.x = x;
			this.y = y;
		}

		public int getX() {
			return x;
		}

		public int getY() {
			return y;
		}
	}

	private static class VortexStep implements Iterable<Dir> {
		private class IteratorImpl implements Iterator<Dir> {
			private int dir = -1;
			private int size = 1;
			private int step;
			private int remainDirStep = 0;
			private int remainSizeStep = 2;

			private IteratorImpl(int step) {
				this.step = step;
			}

			@Override
			public boolean hasNext() {
				return 0 < step;
			}

			@Override
			public Dir next() {
				step--;
				remainDirStep--;
				if (remainDirStep <= 0) {
					remainDirStep = size;
					dir++;
					remainSizeStep--;
					if (remainSizeStep <= 0) {
						remainSizeStep = 2;
						size++;
					}
				}
				dir = dir % dirs.length;
				return dirs[dir];
			}

			@Override
			public void remove() {
				throw new UnsupportedOperationException();
			}
		}

		private final int end;

		private static final Dir[] dirs = new Dir[] {
				Dir.LEFT,//
				Dir.DOWN,//
				Dir.RIGHT,//
				Dir.UP,//
		};

		private VortexStep(int end) {
			super();
			this.end = end;
		}

		@Override
		public Iterator<Dir> iterator() {
			return new IteratorImpl(end);
		}
	}

	private static final int SIZE = 20;

	public static void main(String[] args) throws InterruptedException {
		for (int i = 0; i < 25; i++) {
			boolean[][] map = new boolean[SIZE][SIZE];
			printMap(replace(map, i, 5, 5));
			Thread.sleep(500);
		}
	}

	public static boolean[][] replace(boolean[][] map, int n, int cx, int cy) {
		if (n <= 0) {
			return map;
		}
		boolean f = true;

		map[cx][cy] = f;// 一個目は手動
		VortexStep step = new VortexStep(n - 1);

		for (Dir dir : step) {
			cx += dir.getX();
			cy += dir.getY();

			if (inIn(cx, cy)) {
				map[cy][cx] = f;
			}
		}
		return map;
	}

	private static boolean inIn(int i) {
		return 0 <= i && i < SIZE;
	}

	private static boolean inIn(int x, int y) {
		return inIn(x) && inIn(y);
	}

	private static void printMap(boolean[][] array) {
		for (boolean[] i : array) {
			for (boolean k : i) {
				System.out.print(k ? "#" : ".");
			}
			System.out.println();
		}
	}
}