オフラインリアルタイムどう書く第5回の参考問題のJava解答

RailsOnTiles.java

import static org.junit.Assert.assertEquals;

import org.junit.Test;

/**
 * 3x3マスの各位置のタイル。東西南北に位置するタイルのindexを持つ
 */
class Tile {
    int northernIndex;
    int easternIndex;
    int sourthernIndex;
    int westernIndex;
    char name;

    Tile(int n, int e, int s, int w, char nm) {
        northernIndex = n;
        easternIndex = e;
        sourthernIndex = s;
        westernIndex = w;
        name = nm;
    }

    /**
     * 東西南北のindexを返す。9の場合はタイルの外
     */
    int get(char bearing) {
        if (bearing == 'N') {
            return northernIndex;
        }
        if (bearing == 'E') {
            return easternIndex;
        }
        if (bearing == 'S') {
            return sourthernIndex;
        }
        return westernIndex;
    }

    @Override
    public String toString() {
        return String.valueOf(name);
    }
}

/**
 * 既定の3つのレール。各方角から入ったときの出口の方角を持つ
 */
class Rail {
    char northernExit;
    char easternExit;
    char sourthernExit;
    char westernExit;

    Rail(char n, char e, char s, char w) {
        northernExit = n;
        easternExit = e;
        sourthernExit = s;
        westernExit = w;
    }

    /**
     * enter方角から入ってきた場合のexit方角を返す
     */
    char getExit(char enter) {
        if (enter == 'N') {
            return northernExit;
        }
        if (enter == 'E') {
            return easternExit;
        }
        if (enter == 'S') {
            return sourthernExit;
        }
        return westernExit;
    }
}

/**
 * 問題: http://nabetani.sakura.ne.jp/hena/ord5railsontiles/
 */
public class RailsOnTiles {

    protected String solve(String input) {
        Rail[] rails = createRails();
        Tile[] tiles = createTiles();

        String result = "";
        result = loop(tiles, rails, 'S', 1, input, result);
        return result;
    }

    protected String loop(Tile[] tiles, Rail[] rails, char bearing, int index,
            String input, String result) {
        if (isOut(index)) {
            return result;
        }
        result += tiles[index].toString();
        int railId = Integer.valueOf(String.valueOf(input.charAt(index)));
        Rail rail = rails[railId];
        char exitBearing = rail.getExit(invert(bearing)); // 前回の出口の方角を反転して、入口として与え、次の出口の方角を得る
        int nextIndex = tiles[index].get(exitBearing); // 出て行く方角のindexを得る
        return loop(tiles, rails, exitBearing, nextIndex, input, result);
    }

    protected char invert(char c) {
        if (c == 'N') {
            return 'S';
        }
        if (c == 'E') {
            return 'W';
        }
        if (c == 'S') {
            return 'N';
        }
        return 'E';
    }

    protected boolean isOut(int i) {
        return 8 < i ? true : false;
    }

    protected Rail[] createRails() {
        Rail[] result = new Rail[3];
        result[0] = new Rail('S', 'W', 'N', 'E');
        result[1] = new Rail('E', 'N', 'W', 'S');
        result[2] = new Rail('W', 'S', 'E', 'N');
        return result;
    }

    protected Tile[] createTiles() {
        Tile[] result = new Tile[9];
        result[0] = new Tile(9, 1, 3, 9, 'A');
        result[1] = new Tile(9, 2, 4, 0, 'B');
        result[2] = new Tile(9, 9, 5, 1, 'C');
        result[3] = new Tile(0, 4, 6, 9, 'D');
        result[4] = new Tile(1, 5, 7, 3, 'E');
        result[5] = new Tile(2, 9, 8, 4, 'F');
        result[6] = new Tile(3, 7, 9, 9, 'G');
        result[7] = new Tile(4, 8, 9, 6, 'H');
        result[8] = new Tile(5, 9, 9, 7, 'I');
        return result;
    }

    public static void main(String[] args) {
        RailsOnTiles rot = new RailsOnTiles();
        System.out.println(rot.solve("101221102"));
    }

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

    @Test
    public void testRailsOnTiles() throws Exception {
        /* #0 */test("101221102", "BEDGHIFEH");
        /* #1 */test("000000000", "BEH");
        /* #2 */test("111111111", "BCF");
        /* #3 */test("222222222", "BAD");
        /* #4 */test("000211112", "BEFIHEDGH");
        /* #5 */test("221011102", "BADGHIFEBCF");
        /* #6 */test("201100112", "BEHIFCBADEF");
        /* #7 */test("000111222", "BEFIH");
        /* #8 */test("012012012", "BC");
        /* #9 */test("201120111", "BEDABCFI");
        /* #10 */test("220111122", "BADEHGD");
        /* #11 */test("221011022", "BADG");
        /* #12 */test("111000112", "BCFIHEBA");
        /* #13 */test("001211001", "BEFI");
        /* #14 */test("111222012", "BCFEHIF");
        /* #15 */test("220111211", "BADEHI");
        /* #16 */test("211212212", "BCFEBAD");
        /* #17 */test("002112210", "BEFC");
        /* #18 */test("001010221", "BEF");
        /* #19 */test("100211002", "BEFIHG");
        /* #20 */test("201212121", "BEFCBAD");
    }
}