第7回オフラインリアルタイムどう書く（Java解答）

SelectChair.java

import static org.junit.Assert.assertEquals;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;

import org.junit.Test;

/**
 * 問題: http://qiita.com/items/4364285801d1c9f370a1
 */
public class SelectChair {

    protected final char EMPTY = '-';

    public String solve(final String string) throws IllegalArgumentException {
        String[] split = string.split(":");
	char[] chairs = new char[Integer.valueOf(split[0])];
	Arrays.fill(chairs, EMPTY);

        char[] inOut = split[1].toCharArray();
        for (char each : inOut) {
            if (Character.isUpperCase(each)) {
                int recomended = searchChair(chairs);
                chairs[recomended] = each;
            } else {
                int awayIndex = awayChair(chairs, each);
                chairs[awayIndex] = EMPTY;
            }
        }
        String result = "";
        for (char each : chairs) {
            result += each;
        }
        return result;
    }

    protected int searchChair(final char[] chairs) {
        List<Integer> secondary = new ArrayList<>();
        List<Integer> guttari = new ArrayList<>();

        for (int i = 0; i < chairs.length; i++) {
            char tmpChair = chairs[i];
            if (tmpChair == EMPTY) {
                if (chairs.length == 1) {
                    return i;
                } else if ((i == 0 && EMPTY == chairs[i + 1])
                        || (i == chairs.length - 1 && EMPTY == chairs[i - 1])) {
                    return i;
                } else if ((i == 0 && EMPTY != chairs[i + 1])
                        || (i == chairs.length - 1 && EMPTY != chairs[i - 1])) {
                    secondary.add(i);
                } else if (EMPTY == chairs[i + 1] && EMPTY == chairs[i - 1]) {
		    return i;
		} else if (EMPTY == chairs[i + 1] || EMPTY == chairs[i - 1]) {
		    secondary.add(i);
		} else {
		    guttari.add(i);
		}
            }
        }

        if (secondary.isEmpty() == false) {
            return Collections.min(secondary);
        } else if (guttari.isEmpty() == false) {
            return Collections.min(guttari);
        }
        return new IllegalArgumentException("There are no seats left.");
    }

    protected int awayChair(final char[] chairs, final char c) 
			throws IllegalArgumentException {
        for (int i = 0; i < chairs.length; i++) {
            if (chairs[i] == Character.toUpperCase(c)) {
                return i;
            }
        }
	throw new IllegalArgumentException(Character.toUpperCase(c)
		+ "　hasn't seated.");
    }


    @Test
    public void testSelectChairs() throws Exception {
        /* 1 */test("6:NABEbBZn", "-ZAB-E");
        /* 2 */test("1:A", "A");
        /* 3 */test("1:Aa", "-");
        /* 4 */test("2:AB", "AB");
        /* 5 */test("2:AaB", "B-");
        /* 6 */test("2:AZa", "-Z");
        /* 7 */test("2:AZz", "A-");
        /* 8 */test("3:ABC", "ACB");
        /* 9 */test("3:ABCa", "-CB");
        /* 10 */test("4:ABCD", "ADBC");
        /* 11 */test("4:ABCbBD", "ABDC");
        /* 12 */test("4:ABCDabcA", "-D-A");
        /* 13 */test("5:NEXUS", "NUESX");
        /* 14 */test("5:ZYQMyqY", "ZM-Y-");
        /* 15 */test("5:ABCDbdXYc", "AYX--");
        /* 16 */test("6:FUTSAL", "FAULTS");
        /* 17 */test("6:ABCDEbcBC", "AECB-D");
        /* 18 */test("7:FMTOWNS", "FWMNTSO");
        /* 19 */test("7:ABCDEFGabcdfXYZ", "YE-X-GZ");
        /* 20 */test("10:ABCDEFGHIJ", "AGBHCIDJEF");
    }

    protected void test(String in, String out) throws Exception {
        SelectChair sc = new SelectChair();
        assertEquals(out, sc.solve(in));
    }
}