distance between tiles

[kaputt]

Hi, I'm newbie with the ants. I'm just downloaded the Java's starter package. I've found this on the source code that I don't understand:
Why the distance is rowDelta * rowDelta + colDelta * colDelta?
I think that the distance should be rowDelta + colDelta, isn't it?

The starter package looks like this:

Code: Select all

   /**
     * Calculates distance between two locations on the game map.
     *
     * @param t1 one location on the game map
     * @param t2 another location on the game map
     *
     * @return distance between <code>t1</code> and <code>t2</code>
     */
    public int getDistance(Tile t1, Tile t2) {
        int rowDelta = Math.abs(t1.getRow() - t2.getRow());
        int colDelta = Math.abs(t1.getCol() - t2.getCol());
        rowDelta = Math.min(rowDelta, rows - rowDelta);
        colDelta = Math.min(colDelta, cols - colDelta);
        return rowDelta * rowDelta + colDelta * colDelta; // is that right?
    }


[athena]

That's the direct distance squared. It is useful for checking vision and attack range. The reason for squaring the distance is to avoid the expensive sqrt call (sqrt[rowDelta^2+colDelta^2]).

In other cases you will need the manhatten distance which is rowDelta + colDelta which is the amount of turns it would take an ant to move between two specific locations.

[kaputt]

I've just understood. It's like the view radius, attack radius and spwan radius that are squared too.

I will rename the distance to distance2 (equally that viewRadius2, attackRadius2 and spawnRadius2) and I will implement the distanceManhattan to calculate the amount of turns.

Thank you very much!

[Antonio]

Is there any way to calculate distance between two places? I have faced in a problem that, my teacher has gave me a complicated sum of calculating distance between two places. If you have any solution of this problem, please share that here.