第9回オフラインリアルタイムどう書く参考問題（Java解答）

NumberMake.java

import static org.junit.Assert.assertEquals;

import java.util.ArrayList;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

import org.junit.Test;

/**
 * 問題: http://nabetani.sakura.ne.jp/hena/ord9nummake/
 */
public class NumberMake {

  public String solve(String input) {
		int order = Integer.valueOf(input.split(":")[0]);
		String cards = input.split(":")[1];
		Set<String> cardsSet = getCardsSet(cards);

		Set<String> cardSet = new HashSet<>();
		for (String each : cardsSet) {
			Set<String> tmpSet = makeNum("", each);
			cardSet.addAll(tmpSet);
		}
		cardSet = checkZero(cards, cardSet);

		List<String> cardList = new ArrayList<>(cardSet);
		Collections.sort(cardList);
		if (cardList.size() < order) {
			return "-";
		}
		return cardList.get(order - 1);
	}

	protected Set<String> getCardsSet(final String cards) {
		Set<String> result = new HashSet<>();
		result.add(cards);
		String tmp = cards;
		for (int i = 0; i < getSixNum(cards); i++) {
			tmp = tmp.replaceFirst("6", "9");
			result.add(tmp);
		}
		return result;
	}

	protected int getSixNum(String cards) {
		int result = 0;
		for (int i = 0; i < cards.length(); i++) {
			if (cards.charAt(i) == '6') {
				result++;
			}
		}
		return result;
	}

	protected Set<String> makeNum(final String card, String cards) {
		Set<String> result = new HashSet<>();

		for (int i = 0; i < cards.length(); i++) {
			String tmpCard = card;
			tmpCard += cards.charAt(i);

			String next = "";
			if (0 < i) {
				next += cards.substring(0, i);
			}
			if (i < cards.length() - 1) {
				next += cards.substring(i + 1);
			}
			// System.out.println("card: " + tmpCard + ", next: " + next);
			if (tmpCard.length() < 4) {
				Set<String> tmp = makeNum(tmpCard, next);
				result.addAll(tmp);
			} else {
				result.add(tmpCard);
			}
		}
		return result;
	}

	protected Set<String> checkZero(String cards, Set<String> cardList) {
		Set<String> result = new HashSet<>();
		for (String string : cardList) {
			if (string.startsWith("0") == false) {
				result.add(string);
			}
		}
		return result;
	}

	protected void test(String input, String expected) {
		NumberMake nm = new NumberMake();
		assertEquals(expected, nm.solve(input));
	}

	@Test
	public void testName() throws Exception {
		/* 0 */test("13:01167", "1109");
		/* 1 */test("1:1234", "1234");
		/* 2 */test("2:1234", "1243");
		/* 3 */test("7:1234", "2134");
		/* 4 */test("24:1234", "4321");
		/* 5 */test("25:1234", "-");
		/* 6 */test("2:1116", "1119");
		/* 7 */test("2:0116", "1019");
		/* 8 */test("3:6666", "6696");
		/* 9 */test("16:6666", "9999");
		/* 10 */test("10:01267", "1097");
		/* 11 */test("14:111167", "1671");
		/* 12 */test("1:1111", "1111");
		/* 13 */test("2:1111", "-");
		/* 14 */test("1:666633", "3366");
		/* 15 */test("72:666611", "9999");
		/* 16 */test("73:666622", "-");
		/* 17 */test("1:666600", "6006");
		/* 18 */test("52:666600", "9999");
		/* 19 */test("53:666600", "-");
		/* 20 */test("25:06688", "8086");
		/* 21 */test("93:02566", "6502");
		/* 22 */test("11:06688", "6809");
		/* 23 */test("169:01268", "9801");
		/* 24 */test("174:01268", "9821");
		/* 25 */test("66:012288", "8201");
	}
}