src/main/java/ch/zhaw/pm2/racetrack/Game.java

@@ -141,8 +141,58 @@ public class Game implements GameSpecification {
      */
     @Override
     public List<PositionVector> calculatePath(PositionVector startPosition, PositionVector endPosition) {
-        // TODO: implementation
-        throw new UnsupportedOperationException();
+        ArrayList pathList = new ArrayList<PositionVector>();
+        // Use Bresenham's algorithm to determine positions.
+        int x = startPosition.getX();
+        int y = startPosition.getY();
+
+        // Relative Distance (x & y axis) between end- and starting position
+        int diffX = endPosition.getX() - startPosition.getY();
+        int diffY = endPosition.getY() - startPosition.getY();
+
+        // Absolute distance (x & y axis) between end- and starting position
+        int distX = Math.abs(diffX);
+        int distY = Math.abs(diffY);
+
+        // Direction of vector on x & y axis (-1: to left/down, 0: none, +1 : to right/up)
+        int dirX = Integer.signum(diffX);
+        int dirY = Integer.signum(diffY);
+
+        // Determine which axis is the fast direction and set parallel/diagonal step values
+        int parallelStepX, parallelStepY;
+        int diagonalStepX, diagonalStepY;
+        int distanceSlowAxis, distanceFastAxis;
+        if (distX > distY) {
+            // x axis is the 'fast' direction
+            parallelStepX = dirX; parallelStepY = 0; // parallel step only moves in x direction
+            diagonalStepX = dirX; diagonalStepY = dirY; // diagonal step moves in both directions
+            distanceSlowAxis = distY;
+            distanceFastAxis = distX;
+        } else {
+            // y axis is the 'fast' direction
+            parallelStepX = 0; parallelStepY = dirY; // parallel step only moves in y direction
+            diagonalStepX = dirX; diagonalStepY = dirY; // diagonal step moves in both directions
+            distanceSlowAxis = distX;
+            distanceFastAxis = distY;
+        }
+
+        int error = distanceFastAxis/2;
+        for(int step = 0; step < distanceFastAxis; step ++) {
+            error -= distanceSlowAxis;
+            if (error < 0) {
+                error += distanceFastAxis; // correct error value to be positive again
+                // step into slow direction; diagonal step
+                x += diagonalStepX;
+                y += diagonalStepY;
+            } else {
+                // step into fast direction; parallel step
+                x += parallelStepX;
+                y += parallelStepY;
+            }
+
+        pathList.add(new PositionVector(x,y));
+        }
+        return pathList;
     }