Knight's tour algorithm with adjacency-lists

Question

I'm trying to solve the Knight's tour problem in Java. My goal is to calculate all possible tours of a horse on a chessboard with any dimension. What I have tried to use is an adjadency-lists data structure. The problem now, is that I know which squares are adjacent to a square, but I don't know what direction the adjacent square is in. How would I fix this?

Answer 1

Here's just a rough outline of what you should do:

1. Make a "Square" class with fields for up, down, left, and right (plus accessor and modifier methods)
2. Make a "Chessboard" class to store all the squares and set them up.
3. Make a "Knight" class to move around the chessboard (and check if moves are valid).
4. Finally, create a driver class that searches and stores how to move the Knights around.

Sample Square class:

public class Square
{
    public final Square up;
    public final Square down;
    public final Square left;
    public final Square right;
    public Square(Square up, Square down, Square left, Square right)
    {
        this.up=up;
        this.down=down;
        this.left=left;
        this.right=right;
    }
    public Square getUp(){return up;}
    public Square getDown(){return down;}
    public Square getLeft(){return left;}
    public Square getRight(){return right;}
}

Sample Knight class:

public class Knight
{
    private Square mySquare;

    public Knight(Square start)
    {
        mySquare = start;
    }

    /*  7 0
     * 6    1
     * 
     * 5    2
     *  4 3   
     */
    public boolean move(int dir)
    {
        switch(dir)
        {
        case 0: try{
           mySquare=mySquare.getUp().getUp().getRight(); return true;
        } catch (NullPointerException e) {return false}
        case 1: try{
           mySquare=mySquare.getUp().getRight().getRight(); return true;
        } catch (NullPointerException e) {return false}
        case 2: try{
           mySquare=mySquare.getDown().getRight().getRight(); return true;
        } catch (NullPointerException e) {return false}
        case 3: try{
           mySquare=mySquare.getDown().getDown().getRight(); return true;
        } catch (NullPointerException e) {return false}
        case 7: try{
           mySquare=mySquare.getUp().getUp().getLeft(); return true;
        } catch (NullPointerException e) {return false}
        case 6: try{
           mySquare=mySquare.getUp().getLeft().getLeft(); return true;
        } catch (NullPointerException e) {return false}
        case 5: try{
           mySquare=mySquare.getDown().getLeft().getLeft(); return true;
        } catch (NullPointerException e) {return false}
        case 4: try{
           mySquare=mySquare.getDown().getDown().getLeft(); return true;
        } catch (NullPointerException e) {return false}
        default: return false;
        }
    }
}