第2回 オフラインリアルタイムどう書くの参考問題: Java解答

SpinImage.java

package sample2;

/**
 * 問題: http://qiita.com/items/9d80de41903775296ca6
 */
public class SpinImage {

	protected String execute(String string) {

		String[] split = string.split(":");
		final int imageLength = Integer.valueOf(split[0]);

		String originHex = split[1];
		final int hexLength = originHex.length();

		String binaryString = "";
		for (int i = 0; i < hexLength; i++) {
			char c = originHex.charAt(i);
			int dec = Integer.parseInt(String.valueOf(c), 16);

			// 左端を0パディングした4桁の二進数に変換
			String bin = Integer.toBinaryString(dec);
			for (int k = bin.length(); k < 4; k++) {
				binaryString += "0";
			}
			binaryString += bin;
		}
		final int binaryStrLength = binaryString.length();

		// 画像に不要な右端のbitを捨てる
		if (imageLength * imageLength < binaryString.length()) {
			binaryString = binaryString.substring(0, imageLength * imageLength);
		}

		// 回転前の画像
		int counter = 0;
		char[][] source = new char[imageLength][imageLength];
		for (int i = 0; i < imageLength; i++) {
			for (int k = 0; k < imageLength; k++) {
				source[i][k] = binaryString.charAt(counter++);
			}
		}

		// 回転後の画像
		char[][] dest = new char[imageLength][imageLength];
		int m = 0;
		for (int i = 0; i < imageLength; i++) {
			int p = imageLength - 1;
			for (int k = 0; k < imageLength; k++) {
				dest[i][k] = source[p][m];
				--p;
			}
			m++;
		}

		// 16進表記に戻す準備: 2進表現を1つにまとめる
		String preResult = "";
		for (int i = 0; i < imageLength; i++) {
			for (int k = 0; k < imageLength; k++) {
				preResult += dest[i][k];
			}
		}

		// 2進表現の末尾に、16進変換に必要な0を継ぎ足す
		for (int i = preResult.length(); i < binaryStrLength; i++) {
			preResult += "0";
		}

		String hexString = "";
		for (int i = 0; i < preResult.length(); i += 4) {
			String s = "";
			if (i + 4 < preResult.length()) {
				s += preResult.substring(i, i + 4);
			} else {
				s += preResult.substring(i);
			}
			int parseInt = Integer.parseInt(s, 2);
			hexString += Integer.toHexString(parseInt);
		}

		StringBuilder result = new StringBuilder(String.valueOf(imageLength));
		result.append(":");

		// 16進表記を元の桁数に揃える（先頭に0パディング）
		for (int i = preResult.length(); i < hexLength; i++) {
			result.append("0");
		}
		result.append(hexString);
		return new String(result);
	}

	public static void main(String[] args) {

		// すべてのテストデータは、SpinImageTest.javaを参照。
		SpinImage spin = new SpinImage();
		System.out.println(spin.execute("6:123456789"));
	}
}

SpinImageTest.java

package sample2;

import static org.junit.Assert.assertEquals;

import org.junit.Test;

/**
 * テストデータ: http://qiita.com/items/9d80de41903775296ca6
 */
public class SpinImageTest {
	SpinImage spin;

	@Test
	public void testExecute() throws Exception {
		spin = new SpinImage();
		assertEquals("3:5b8 → 3:de0", "3:de0", spin.execute("3:5b8"));
		assertEquals("1:8 → 1:8", "1:8", spin.execute("1:8"));
		assertEquals("2:8 → 2:4", "2:4", spin.execute("2:8"));
		assertEquals("2:4 → 2:1", "2:1", spin.execute("2:4"));
		assertEquals("2:1 → 2:2", "2:2", spin.execute("2:1"));
		assertEquals("3:5d0 → 3:5d0", "3:5d0", spin.execute("3:5d0"));
		assertEquals("4:1234 → 4:0865", "4:0865", spin.execute("4:1234"));
		assertEquals("5:22a2a20 → 5:22a2a20", "5:22a2a20",
				spin.execute("5:22a2a20"));
		assertEquals("5:1234567 → 5:25b0540", "5:25b0540",
				spin.execute("5:1234567"));
		assertEquals("6:123456789 → 6:09cc196a6", "6:09cc196a6",
				spin.execute("6:123456789"));
		assertEquals("7:123456789abcd → 7:f1a206734b258", "7:f1a206734b258",
				spin.execute("7:123456789abcd"));
		assertEquals("7:fffffffffffff → 7:ffffffffffff8", "7:ffffffffffff8",
				spin.execute("7:fffffffffffff"));
		assertEquals("7:fdfbf7efdfbf0 → 7:ffffffffffc00", "7:ffffffffffc00",
				spin.execute("7:fdfbf7efdfbf0"));
		assertEquals("8:123456789abcdef1 → 8:f0ccaaff78665580",
				"8:f0ccaaff78665580", spin.execute("8:123456789abcdef1"));
		assertEquals("9:112233445566778899aab → 9:b23da9011d22daf005d40",
				"9:b23da9011d22daf005d40",
				spin.execute("9:112233445566778899aab"));
	}
}