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A. Nell
A. Nell

Reputation: 11

8-Puzzle Java Algorithm Puzzle

I have been working on a 8-puzzle for class, and getting frustrated a bit checking out code. I need to write code regarding left, right, up, and down movement. When I remove the right, the code gives a "index out of bounds -1" error, for the double array, after expanding to get the successor nodes and adding them. Is the code below proper for going through the maze/successors, that returns the child to the parent? Is something wrong in the code for left, up, down, and right?

When I return several tests, I do see that the movement of the 0 moves to the right, and then down when it reaches the edge, so I am not sure if the code below is actually functioning correct, or if something in it needs to be changed.

The puzzle needs to give an output of:

1 2 3

4 5 6

7 8 0

Typical output shows:

1 7 8

5 4 2

3 6 0

As such, pathing seems to be wrong and I believe it is related to the movement code below, but I am unsure. The question I have is the code below accurate, does something need to be changed in it? Is something causing the ArrayIndexoutOfBounds -1 related to this, or is it something else?

ArrayList<Node> successors = new ArrayList<Node>();
//generate a successor from moving the 0 to the right 
if (col < size-1) {
    int[][] right = Board.copyBoard(board);
    right[row][col] = right[row][col + 1];
    right[row][col+1] = 0;                  
    successors.add(new Node(right)); 
} else if (col < size - 1) {
    int[][] left = Board.copyBoard(board);
    left[row][col] = left[row][col-1];
    left[row][col-1] = 0;
    successors.add(new Node(left));
} else if (row < size-1) {
    int[][] down = Board.copyBoard(board);
    down[row][col] = down[row + 1][col];
    down[row + 1][col] = 0;                 
    successors.add(new Node(down)); 
} else if (row < size - 1) {
    int[][] up = Board.copyBoard(board);
    up[row][col] = up[row-1][col];
    up[row-1][col] = 0;
    successors.add(new Node(up));
}

return successors;

Upvotes: 1

Views: 428

Answers (1)

SteveR
SteveR

Reputation: 613

At the moment, your code checks col < size -1 for both left and right movements, and similarly for up and down. The second condition should be col > 0 and the last one row >0

Upvotes: 3

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