An algorithm to space out overlapping rectangles?

I think this solution is quite similar to the one given by cape1232, but it's already implemented, so worth checking out :)

Follow to this reddit discussion: http://www.reddit.com/r/gamedev/comments/1dlwc4/procedural_dungeon_generation_algorithm_explained/ and check out the description and implementation. There's no source code available, so here's my approach to this problem in AS3 (works exactly the same, but keeps rectangles snapped to grid's resolution):

public class RoomSeparator extends AbstractAction {
    public function RoomSeparator(name:String = "Room Separator") {
        super(name);
    }

    override public function get finished():Boolean { return _step == 1; }

    override public function step():void {
        const repelDecayCoefficient:Number = 1.0;

        _step = 1;

        var count:int = _activeRoomContainer.children.length;
        for(var i:int = 0; i < count; i++) {
            var room:Room           = _activeRoomContainer.children[i];
            var center:Vector3D     = new Vector3D(room.x + room.width / 2, room.y + room.height / 2);
            var velocity:Vector3D   = new Vector3D();

            for(var j:int = 0; j < count; j++) {
                if(i == j)
                    continue;

                var otherRoom:Room = _activeRoomContainer.children[j];
                var intersection:Rectangle = GeomUtil.rectangleIntersection(room.createRectangle(), otherRoom.createRectangle());

                if(intersection == null || intersection.width == 0 || intersection.height == 0)
                    continue;

                var otherCenter:Vector3D = new Vector3D(otherRoom.x + otherRoom.width / 2, otherRoom.y + otherRoom.height / 2);
                var diff:Vector3D = center.subtract(otherCenter);

                if(diff.length > 0) {
                    var scale:Number = repelDecayCoefficient / diff.lengthSquared;
                    diff.normalize();
                    diff.scaleBy(scale);

                    velocity = velocity.add(diff);
                }
            }

            if(velocity.length > 0) {
                _step = 0;
                velocity.normalize();

                room.x += Math.abs(velocity.x) < 0.5 ? 0 : velocity.x > 0 ? _resolution : -_resolution;
                room.y += Math.abs(velocity.y) < 0.5 ? 0 : velocity.y > 0 ? _resolution : -_resolution;
            }
        }
    }
}

Here is a version that takes cape1232's answer and is a standalone runnable example for Java:

public class Rectangles extends JPanel {

    List<Rectangle2D> rectangles = new ArrayList<Rectangle2D>();
    {
        // x,y,w,h
        rectangles.add(new Rectangle2D.Float(300, 50, 50, 50));

        rectangles.add(new Rectangle2D.Float(300, 50, 20, 50));

        rectangles.add(new Rectangle2D.Float(100, 100, 100, 50));

        rectangles.add(new Rectangle2D.Float(120, 200, 50, 50));

        rectangles.add(new Rectangle2D.Float(150, 130, 100, 100));

        rectangles.add(new Rectangle2D.Float(0, 100, 100, 50));

        for (int i = 0; i < 10; i++) {
            for (int j = 0; j < 10; j++) {
                rectangles.add(new Rectangle2D.Float(i * 40, j * 40, 20, 20));
            }
        }
    }

    List<Rectangle2D> rectanglesToDraw;

    protected void reset() {
        rectanglesToDraw = rectangles;

        this.repaint();
    }

    private List<Rectangle2D> findIntersections(Rectangle2D rect, List<Rectangle2D> rectList) {

        ArrayList<Rectangle2D> intersections = new ArrayList<Rectangle2D>();

        for (Rectangle2D intersectingRect : rectList) {
            if (!rect.equals(intersectingRect) && intersectingRect.intersects(rect)) {
                intersections.add(intersectingRect);
            }
        }

        return intersections;
    }

    protected void fix() {
        rectanglesToDraw = new ArrayList<Rectangle2D>();

        for (Rectangle2D rect : rectangles) {
            Rectangle2D copyRect = new Rectangle2D.Double();
            copyRect.setRect(rect);
            rectanglesToDraw.add(copyRect);
        }

        // Find the center C of the bounding box of your rectangles.
        Rectangle2D surroundRect = surroundingRect(rectanglesToDraw);
        Point center = new Point((int) surroundRect.getCenterX(), (int) surroundRect.getCenterY());

        int movementFactor = 5;

        boolean hasIntersections = true;

        while (hasIntersections) {

            hasIntersections = false;

            for (Rectangle2D rect : rectanglesToDraw) {

                // Find all the rectangles R' that overlap R.
                List<Rectangle2D> intersectingRects = findIntersections(rect, rectanglesToDraw);

                if (intersectingRects.size() > 0) {

                    // Define a movement vector v.
                    Point movementVector = new Point(0, 0);

                    Point centerR = new Point((int) rect.getCenterX(), (int) rect.getCenterY());

                    // For each rectangle R that overlaps another.
                    for (Rectangle2D rPrime : intersectingRects) {
                        Point centerRPrime = new Point((int) rPrime.getCenterX(), (int) rPrime.getCenterY());

                        int xTrans = (int) (centerR.getX() - centerRPrime.getX());
                        int yTrans = (int) (centerR.getY() - centerRPrime.getY());

                        // Add a vector to v proportional to the vector between the center of R and R'.
                        movementVector.translate(xTrans < 0 ? -movementFactor : movementFactor,
                                yTrans < 0 ? -movementFactor : movementFactor);

                    }

                    int xTrans = (int) (centerR.getX() - center.getX());
                    int yTrans = (int) (centerR.getY() - center.getY());

                    // Add a vector to v proportional to the vector between C and the center of R.
                    movementVector.translate(xTrans < 0 ? -movementFactor : movementFactor,
                            yTrans < 0 ? -movementFactor : movementFactor);

                    // Move R by v.
                    rect.setRect(rect.getX() + movementVector.getX(), rect.getY() + movementVector.getY(),
                            rect.getWidth(), rect.getHeight());

                    // Repeat until nothing overlaps.
                    hasIntersections = true;
                }

            }
        }
        this.repaint();
    }

    private Rectangle2D surroundingRect(List<Rectangle2D> rectangles) {

        Point topLeft = null;
        Point bottomRight = null;

        for (Rectangle2D rect : rectangles) {
            if (topLeft == null) {
                topLeft = new Point((int) rect.getMinX(), (int) rect.getMinY());
            } else {
                if (rect.getMinX() < topLeft.getX()) {
                    topLeft.setLocation((int) rect.getMinX(), topLeft.getY());
                }

                if (rect.getMinY() < topLeft.getY()) {
                    topLeft.setLocation(topLeft.getX(), (int) rect.getMinY());
                }
            }

            if (bottomRight == null) {
                bottomRight = new Point((int) rect.getMaxX(), (int) rect.getMaxY());
            } else {
                if (rect.getMaxX() > bottomRight.getX()) {
                    bottomRight.setLocation((int) rect.getMaxX(), bottomRight.getY());
                }

                if (rect.getMaxY() > bottomRight.getY()) {
                    bottomRight.setLocation(bottomRight.getX(), (int) rect.getMaxY());
                }
            }
        }

        return new Rectangle2D.Double(topLeft.getX(), topLeft.getY(), bottomRight.getX() - topLeft.getX(),
                bottomRight.getY() - topLeft.getY());
    }

    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2d = (Graphics2D) g;

        for (Rectangle2D entry : rectanglesToDraw) {
            g2d.setStroke(new BasicStroke(1));
            // g2d.fillRect((int) entry.getX(), (int) entry.getY(), (int) entry.getWidth(),
            // (int) entry.getHeight());
            g2d.draw(entry);
        }

    }

    protected static void createAndShowGUI() {
        Rectangles rects = new Rectangles();

        rects.reset();

        JFrame frame = new JFrame("Rectangles");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLayout(new BorderLayout());
        frame.add(rects, BorderLayout.CENTER);

        JPanel buttonsPanel = new JPanel();

        JButton fix = new JButton("Fix");

        fix.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                rects.fix();

            }
        });

        JButton resetButton = new JButton("Reset");

        resetButton.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(ActionEvent e) {
                rects.reset();
            }
        });

        buttonsPanel.add(fix);
        buttonsPanel.add(resetButton);

        frame.add(buttonsPanel, BorderLayout.SOUTH);

        frame.setSize(400, 400);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {

            @Override
            public void run() {
                createAndShowGUI();

            }
        });
    }

}