Separating bichromatic point sets by two disjoint isothetic rectangles

Given a set P of red points and a set Q of blue points in a plane with total size n, we investigate the problem of nding two disjoint isothetic rectangles containing all the points of Q, avoiding any points of P. Such rectangles are called two separating disjoint isothetic rectangles. We rst compute two separating disjoint axisaligned rectangles in O(n log n) time. Then, we relax the axis-aligned constraint and report all combinatorially dierent two separating disjoint isothetic rectangles. To compute these rectangles, we introduce some events by rotating the coordinate system and processing these events. Computing and processing all of the events are done in O(n2 log n) time. Thus, our algorithm reports all combinatorially dierent separating rectangles in O(n2 log n) time.