3

コードは私には問題ないように思えますが、出力が短すぎて、はいのはずの答えがいいえです (a,0 から始めて、ナイトはボード全体をツアーできるはずです)。

ちなみに、私のpositionsVisted配列が [9][9] になっているのは、出力と一致するように値を 1 ～ 8 にしたかったからです。

public class KnightChessRiddle {
static // given a chess board and a 0,0 starting point, can a knight pass through
// all the the squares without passing
// a square twice

int[][] positionsVisited = new int[9][9];
static int positionX = 1;
static int positionY = 1;
boolean stop = false;
static boolean continUe = false;
static int moveCounter = -1;

public static void main(String[] args) {
    if (recursive(1, 1, 0)) {
        System.out.println("yes");
    }
    else System.out.println("no");
}

public static boolean recursive(int x, int y, int moveType){


    if (x>8||x<=0||y>8||y<=0) return false;
    if (positionsVisited[x][y]==1) {
        return false;
    }
    positionX = x;
    positionY = y;
    positionsVisited[positionX][positionY]++;

    char c;
    c='a';
    switch (positionX) {
    case 1:
        c='a';
        break;
    case 2:
        c='b';
        break;
    case 3:
        c='c';
        break;
    case 4:
        c='d';
        break;
    case 5:
        c='e';
        break;
    case 6:
        c='f';
        break;
    case 7:
        c='g';
        break;
    case 8:
        c='h';
        break;

    default: 
        break;
    }
    moveCounter++;
    System.out.println("doing move "+moveType+" move count: "+moveCounter);
    System.out.println("Knight is in "+ c +","+positionY);

    try {
        Thread.sleep(100);
    } catch (InterruptedException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    if (recursive(positionX+2, positionY+1, 1)) {
        return true;
    }
    else if (recursive(positionX+1, positionY+2, 2) ) {
        return true;
    }
    else if (recursive(positionX+2, positionY-1, 3) ) {
        return true;
    }
    else if (recursive(positionX+1, positionY-2, 4)) {
        return true;
    }
    else if (recursive(positionX-2, positionY+1, 5)) {
        return true;
    }
    else if (recursive(positionX-1, positionY+2, 6)) {
        return true;
    }
    else if (recursive(positionX-2, positionY-1, 7)) {
        return true;
    }
    else if (recursive(positionX-1, positionY-2, 8)) {
        return true;
    }
    else return false;
}

これはプログラムの出力です:

doing move 0 move count: 0
Knight is in a,1
doing move 1 move count: 1
Knight is in c,2
doing move 1 move count: 2
Knight is in e,3
doing move 1 move count: 3
Knight is in g,4
doing move 2 move count: 4
Knight is in h,6
doing move 5 move count: 5
Knight is in f,7
doing move 1 move count: 6
Knight is in h,8
doing move 8 move count: 7
Knight is in g,6
doing move 4 move count: 8
Knight is in h,4
doing move 5 move count: 9
Knight is in f,5
doing move 2 move count: 10
Knight is in g,7
doing move 4 move count: 11
Knight is in h,5
doing move 5 move count: 12
Knight is in f,6
doing move 1 move count: 13
Knight is in h,7
doing move 5 move count: 14
Knight is in f,8
doing move 7 move count: 15
Knight is in d,7
doing move 4 move count: 16
Knight is in e,5
doing move 4 move count: 17
Knight is in f,3
doing move 2 move count: 18
Knight is in g,5
doing move 4 move count: 19
Knight is in h,3
doing move 5 move count: 20
Knight is in f,4
doing move 4 move count: 21
Knight is in g,2
doing move 7 move count: 22
Knight is in e,1
doing move 6 move count: 23
Knight is in d,3
doing move 3 move count: 24
Knight is in f,2
doing move 3 move count: 25
Knight is in h,1
doing move 6 move count: 26
Knight is in g,3
doing move 5 move count: 27
Knight is in e,4
doing move 5 move count: 28
Knight is in c,5
doing move 1 move count: 29
Knight is in e,6
doing move 5 move count: 30
Knight is in c,7
doing move 1 move count: 31
Knight is in e,8
doing move 8 move count: 32
Knight is in d,6
doing move 5 move count: 33
Knight is in b,7
doing move 1 move count: 34
Knight is in d,8
doing move 8 move count: 35
Knight is in c,6
doing move 1 move count: 36
Knight is in e,7
doing move 1 move count: 37
Knight is in g,8
no
4

2 に答える 2

0

「すべてが訪問されました」チェックの問題を除いて、クラスフィールドにある少なくとも1つの問題が見られます。アルゴリズムが再帰の 1 つの分岐を通過すると、いくつかの四角形が訪問済みとしてマークされます。この情報はクラス フィールドであるため、現在の分岐に失敗して別の分岐を開始すると、以前の試行からのすべての無効な情報が表示されます。

とをメソッドの引数として渡しpositionsVisitedてクラス フィールドから削除すると、各メソッド呼び出しに独自の実際のコピーが作成されるのでしょうか。positionXpositionY

最終版

public class KnightChessRiddle {

    private final static Map<Integer, Character> letters = new HashMap<>();

    static {
        letters.put(0, 'a');
        letters.put(1, 'b');
        letters.put(2, 'c');
        letters.put(3, 'd');
        letters.put(4, 'e');
        letters.put(5, 'f');
    }

    public static void main(String[] args) {
        if (recursive(0, 0, 0, new boolean[6][6], 1, "")) {
            System.out.println("yes");
        } else {
            System.out.println("no");
        }
    }

    private static boolean allVisited(boolean[][] positionsVisited) {
        for (int i = 0; i < positionsVisited.length; i++) {
            for (int j = 0; j < positionsVisited.length; j++) {
                if (!positionsVisited[i][j]) {
                    return false;
                }
            }
        }
        return true;
    }

    private static boolean recursive(int positionX, int positionY, int moveType,
            boolean[][] positionsVisited, int moveCounter, String currentMoves) {

        // checks
        if (allVisited(positionsVisited)) {
            System.out.println(currentMoves);
            return true;
        }

        if (positionX > 5 || positionX < 0 || positionY > 5 || positionY < 0) {
            return false;
        }

        if (positionsVisited[positionX][positionY]) {
            return false;
        }

        // make move
        positionsVisited[positionX][positionY] = true;

        char c = letters.get(positionX);
        currentMoves += "" + c + (positionY + 1) + " (move type: " + (moveType + 1) + ")\r\n";

        if (recursive(positionX + 2, positionY + 1, 1, cloneArray(positionsVisited), moveCounter + 1, currentMoves)) {
            return true;
        } else if (recursive(positionX + 1, positionY + 2, 2, cloneArray(positionsVisited), moveCounter + 1, currentMoves)) {
            return true;
        } else if (recursive(positionX + 2, positionY - 1, 3, cloneArray(positionsVisited), moveCounter + 1, currentMoves)) {
            return true;
        } else if (recursive(positionX + 1, positionY - 2, 4, cloneArray(positionsVisited), moveCounter + 1, currentMoves)) {
            return true;
        } else if (recursive(positionX - 2, positionY + 1, 5, cloneArray(positionsVisited), moveCounter + 1, currentMoves)) {
            return true;
        } else if (recursive(positionX - 1, positionY + 2, 6, cloneArray(positionsVisited), moveCounter + 1, currentMoves)) {
            return true;
        } else if (recursive(positionX - 2, positionY - 1, 7, cloneArray(positionsVisited), moveCounter + 1, currentMoves)) {
            return true;
        } else if (recursive(positionX - 1, positionY - 2, 8, cloneArray(positionsVisited), moveCounter + 1, currentMoves)) {
            return true;
        } else {
            return false;
        }

    }

    private static boolean[][] cloneArray(boolean[][] src) {
        boolean[][] newPositions = new boolean[src.length][src.length];
        for (int i = 0; i < src.length; i++) {
            System.arraycopy(src[i], 0, newPositions[i], 0, src[0].length);
        }
        return newPositions;
    } 
}

これは、6x6 ボードを使用した作業バリエーションです。私のマシンでは、8x8 ボードの計算に時間がかかりすぎます。移動の選択をランダム化すると、より高速になる可能性があります。

于 2014-01-02T11:54:56.657 に答える