第11回オフラインリアルタイムどう書く（Java解答）

BitamidaEx.java

package yhpg11;

public class BitamidaEx {

  enum Direction {
		right {
			@Override
			int move(int row, int x) {
				for (int i = x; i < 9; i++) {
					if (BitamidaEx.is(row, i) == false) {
						return i;
					}
				}
				return 8;
			}
		},
		left {
			@Override
			int move(int row, int x) {
				for (int i = x; -1 < i; i--) {
					if (BitamidaEx.is(row, i - 1) == false) {
						return i;
					}
				}
				return 0;
			}
		},
		down {
			@Override
			int move(int row, int x) {
				return x; // do nothing
			}
		};
		abstract int move(int row, int x);
	}

	public String solve(String input) {
		int[] rows = parseRows(input);

		int[] result = new int[9];
		for (int i = 0; i < 9; i++) {
			int beginX = i;
			int x = beginX;
			for (int y = 0; y < 4; y++) {
				int r = rows[y];
				Direction d = decide(r, x);
				x = d.move(r, x);
			}
			result[x] = beginX;
		}

		return format(result);
	}

	String format(int[] result) {
		StringBuilder sb = new StringBuilder();
		for (int i : result) {
			sb.append(String.valueOf(i));
		}
		return new String(sb);
	}

	Direction decide(int row, int x) {
		boolean left = is(row, x - 1);
		boolean current = is(row, x);
		if (left == current) {
			return Direction.down;
		}
		if (left) {
			return Direction.left;
		}
		return Direction.right;
	}

	static boolean is(int row, int index) {
		return ((row >> (7 - index)) & 1) != 0;
	}

	int[] parseRows(String input) {
		String[] split = input.split("-");
		int[] result = new int[4];
		for (int i = 0; i < result.length; i++) {
			result[i] = Integer.parseInt(split[i], 16);
		}
		return result;
	}
}

BitamidaTest.java

package yhpg11;

import static org.junit.Assert.assertArrayEquals;
import static org.junit.Assert.assertEquals;

import org.junit.Before;
import org.junit.Test;

import yhpg11.BitamidaEx.Direction;

public class BitamidaTest {
  BitamidaEx target;

	@Before
	public void setUp() {
		target = new BitamidaEx();
	}

	@Test
	public void testFormat() throws Exception {
		int[] actual = { 0, 1, 2, 3 };
		assertEquals("0123", target.format(actual));
	}

	@Test
	public void testParseRows() throws Exception {
		String actual = "d6-7b-e1-9e";
		int[] expected = { 0xd6, 0x7b, 0xe1, 0x9e };
		assertArrayEquals(expected, target.parseRows(actual));
	}

	public void testDecide(Class<?> clazz, int row, int x) throws Exception {
		assertEquals(clazz, target.decide(row, x).getClass());
	}

	@Test
	public void testDecideRight() throws Exception {
		int actualRow = 0xdb;
		int actualX = 3;
		testDecide(Direction.right.getClass(), actualRow, actualX);
	}

	@Test
	public void testDecideLeft() throws Exception {
		int actualRow = 0xdb;
		int actualX = 2;
		testDecide(Direction.left.getClass(), actualRow, actualX);
	}

	@Test
	public void testDecideDown() throws Exception {
		int actualRow = 0xdb;
		int actualX = 4;
		testDecide(Direction.down.getClass(), actualRow, actualX);
	}

	@Test
	public void testDecideThrough() throws Exception {
		int actualRow = 0xdf;
		int actualX = 4;
		testDecide(Direction.down.getClass(), actualRow, actualX);
	}

	@Test
	public void testMoveRight() throws Exception {
		Direction target = Direction.right;
		assertEquals(2, target.move(0xdb, 0));
	}

	@Test
	public void testMoveLeft() throws Exception {
		Direction target = Direction.left;
		assertEquals(3, target.move(0xdb, 5));
	}

	public void test(String input, String expected) {
		assertEquals(input, target.solve(input), expected);
	}

	@Test
	public void testSolve() throws Exception {
		/* 0 */test("d6-7b-e1-9e", "740631825");
		/* 1 */test("83-4c-20-10", "123805476");
		/* 2 */test("fb-f7-7e-df", "274056813");
		/* 3 */test("55-33-0f-ff", "123456780");
		/* 4 */test("00-00-00-00", "012345678");
		/* 5 */test("00-00-00-55", "021436587");
		/* 6 */test("40-10-04-01", "021436587");
		/* 7 */test("00-00-aa-00", "103254768");
		/* 8 */test("80-20-08-02", "103254768");
		/* 9 */test("ff-7e-3c-18", "876543210");
		/* 10 */test("aa-55-aa-55", "351708264");
		/* 11 */test("55-aa-aa-55", "012345678");
		/* 12 */test("db-24-db-e7", "812543670");
		/* 13 */test("00-01-00-40", "021345687");
		/* 14 */test("00-00-80-00", "102345678");
		/* 15 */test("01-40-00-00", "021345687");
		/* 16 */test("00-00-00-02", "012345768");
		/* 17 */test("00-00-02-00", "012345768");
		/* 18 */test("00-14-00-00", "012436578");
		/* 19 */test("00-00-01-40", "021345687");
		/* 20 */test("00-80-01-00", "102345687");
		/* 21 */test("c8-00-00-81", "120354687");
		/* 22 */test("05-48-08-14", "021435687");
		/* 23 */test("24-05-00-f0", "413205687");
		/* 24 */test("40-08-14-01", "021536487");
		/* 25 */test("18-c8-80-80", "210534678");
		/* 26 */test("1c-88-52-00", "120564738");
		/* 27 */test("ec-dc-67-62", "213468705");
		/* 28 */test("0a-b6-60-e9", "035162784");
		/* 29 */test("52-d6-c6-c2", "120345678");
		/* 30 */test("47-e7-b0-36", "231047658");
		/* 31 */test("0f-85-91-aa", "108263754");
		/* 32 */test("76-b6-ed-f3", "601435782");
		/* 33 */test("f5-5e-f7-3d", "025847163");
		/* 34 */test("dd-e7-fb-f9", "610247538");
		/* 35 */test("8f-f4-af-fd", "583246017");
		/* 36 */test("bf-fb-cb-f7", "105382674");
		/* 37 */test("e5-fd-ff-ff", "512046378");
		/* 38 */test("ef-df-ef-fe", "713205648");
		/* 39 */test("bf-7f-fd-d7", "826437105");
		/* 40 */test("36-ff-df-de", "814527603");
		/* 41 */test("6f-dd-ff-ff", "230685147");
	}
}