Question

我遇到以下代码的一些问题。首先，我似乎无法想象如何阻止这件事走出界限。第二，当代码工作时，它没有正确地添加计数步骤。

package runknightstour;

public class RunKnightsTour 
{
    public static void main(String[] args) 
    {    
        KnightMoves tour = new KnightMoves();     
        tour.runTour();
    }
}

package runknightstour;

public class ChessBoard 
{
    public final int ROWS = 8;
    public final int COLS = 8;
    public final int FRAMESIZE = 12;
    private int[][] board = new int[FRAMESIZE][FRAMESIZE];

    public ChessBoard()
    {
        for (int y = 0; y < board.length; y++) {
            for (int x = 0; x < board[y].length; x++) {
                board[y][x] = -1;
            }
            for (int r = 2; r < ROWS + 2; r++) {
                for (int c = 2; c < COLS + 2; c++) {
                    board[r][c] = 0;
                }
            } 
        }
    }
    public String toString()
    {
        String output = "";
        for (int r = 0; r < FRAMESIZE; r++) {
            for (int c = 0; c < FRAMESIZE; c++) {
                output += board[r][c];   
                output += "\t";
            }
            output += "\n\n";
        }
        return output; 
    }
   /**
    * 
    * @param row
    * @param col
    * @param inStep in the range of 1 - 64
    */      
    public void setSquare(int row, int col, int inStep)
    {
        //  adjust input to match 2 - 9
        row += 1;
       col +=1;
        if (row > 1 && row < 10 && col > 1 && col < 10)
        {
            board[row][col] = inStep;
        }
    }
    public int getSquare (int row, int col)
    {
        return board[row][col];
    }
}
package runknightstour;
import java.util.Random;
import java.util.Scanner;

public class KnightMoves 
{
    public final int COMPLETE_TOUR = 64;
    private ChessBoard kBoard = new ChessBoard();
    private int[][] moves = new int[8][2];
    private int stepNumber;
    private int currentRow;
    private int currentCol;
    private int startRow;
    private int startCol;


    public KnightMoves()
    {
        moves[0][0] = -2; // move 0 row offset
        moves[0][1] = 1; // move 0 col offset

        moves[1][0] = -1; // move 1 row offset
        moves[1][1] = 2; // move 1 col offset

       moves[2][0] = 1; // move 2 row offset
        moves[2][1] = 2; // move 2 col offset

        moves[3][0] = 2; // move 3 row offset
        moves[3][1] = 1; // move 3 col offset

        moves[4][0] = 2; // move 4 row offset
        moves[4][1] = -1; // move 4 col offset

        moves[5][0] = 1; // move 5 row offset
        moves[5][1] = -2; // move 5 col offset

        moves[6][0] = -1; // move 6 row offset
        moves[6][1] = -2; // move 6 col offset

        moves[7][0] = -2; // move 7 row offset
        moves[7][1] = -1; // move 7 col offset

        stepNumber = 0;
        startRow = startCol = 1;
        currentRow = currentCol = 1;  
    }
    /**
     *  Description:  Get the starting board Position (row, col) for the 
     *                KNIGHT from program user
     */
    public void getStartPosition()
    {
        Scanner input = new Scanner(System.in);
        System.out.print("\n enter a starting location for the knight's row ");
        startRow = input.nextInt();
        System.out.print("\n enter a starting location for the knight's col ");
        startCol = input.nextInt();

        kBoard.setSquare(startRow, startCol, 1);

        System.out.println(kBoard);
    }
    /**
    * Mutator: runTour()
    */
    public void runTour()
    {
        getStartPosition();

        // if stepNumber is equal to COMPLETE_TOUR
        // report that the knight made a complete tour
        do {
            takeStep();
        }
        while (stepNumber < 64 && takeStep()== true);

        System.out.println(kBoard);
        System.out.println(toString());       
    }   

    private boolean takeStep()
    {   
        boolean stepTaken = true;
        int random1;
        Random rand = new Random();
        random1 = rand.nextInt(8);
        int tryStepRow =0;
        int tryStepCol=0;
        int attempts =0;
        do {   
            tryStepRow = currentRow + moves[random1][0];
            tryStepCol = currentCol + moves[random1][1];
            if(kBoard.getSquare(tryStepRow,tryStepCol)==0)
            {
                kBoard.setSquare(tryStepRow,tryStepCol, stepNumber++);
                currentRow= tryStepRow;
                currentCol = tryStepCol;
            }
            else 
            {
               attempts++;
            }               
       } while (stepTaken == false && attempts < 200);
        return stepTaken;
    }
    public String toString()
    {
        String whatHappened = "";
        whatHappened += "Starting location: [" + startRow + ", "
      + startCol + "]\n";
        whatHappened += " Tour ended after " + stepNumber + " steps\n";
        whatHappened += "The knight got stuck in location ["
      + (currentRow ) + ", " + (currentCol ) + "]\n";
        return whatHappened;

    } 
}

我收到的示例消息。

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -1
at runknightstour.ChessBoard.getSquare(ChessBoard.java:68)
at runknightstour.KnightMoves.takeStep(KnightMoves.java:101)
at runknightstour.KnightMoves.runTour(KnightMoves.java:80)
at runknightstour.RunKnightsTour.main(RunKnightsTour.java:22)
I:\CSC122\RunKnightsTour\nbproject\build-impl.xml:1039: The following error         occurred while executing this line:
I:\CSC122\RunKnightsTour\nbproject\build-impl.xml:804: Java returned: 1
BUILD FAILED (total time: 2 seconds)

Answer 1

如果您仔细查看函数setSquare()，您会注意到它会进入无限循环，因为row或col上没有给出增量条件。

此外，如果您的board尺寸不够大，那么您最终可能会遇到ArraysOutOfBounds例外情况。

public void setSquare(int row, int col, int inStep)
{
    //  adjust input to match 2 - 9
    row += 1;
    col += 1;
    if (row > 1 && row < 10 && col > 1 && col < 10)
    {
        /* Where are you incrementing row/col? */
        board[row][col] = inStep;
    }
}

Java Knights巡演代码

1 个答案: