Rectangles Covering

Question

I have N rectangles with sides parallel to the x- and y-axes. There is another rectangle, model. I need to create an algorithm that can tell whether the

Answer 1

You're on the right track with the sweep line. Conceptually, we want to detect when intersection of the model with the sweep line is not covered by the other rectangles. The high-level template is to break each rectangle into a "left edge" and a "right edge" event, sort the events by x coordinate (putting lefts before rights if the rectangles are closed and rights before lefts if they are open), and then process each event in O(log n) time. This is basically homework, so I will say no more.