Converting Vertex[] to graph

Question

I am making a Pac-Man game and I am currently working on the ghosts AI. I am planning on using Dijkstra's algorithm for the pathfinding. My problem is that when my game is loaded the vertices for the graph are stored in a matrix. I am trying to assign each vertex all of its edges like this

    for(int x = 0; x<40; x++)
    {
        for(int y = 0; y<40; y++)
        {
            Vertex vertex = map[x][y];
            vertex.adjacencies = new Edge[]{new Edge(map[x-1][y], 1), new Edge(map[x+1][y], 1), new Edge(map[x][y-1], 1), new Edge(map[x][y+1], 1)};
        }
    }

the problem is that it sometimes throws an array out of bounds exception. How would I fix this without putting in tons of if statements to check if the current vertex is on the edge of the graph?

Answer 1

One easy way is to include a non-traversable border around the edges.

For example, if your actual map is 40x40, you can declare a 42x42 array. Rows 0 and n would be non-traversable, as would be columns 0 and n.

You'd still need to handle cylindrical travel of the pacman between left and right sides.

Answer 2

You should start your loop with a "border" of 1, like this:

for(int x = 1; x < 39; x++)

because, when you create your edges with map[x-1][y] with a x started to 0, it take -1 as array index, so it throw an Array Out of Bounds exception.