Here is the summery:
#0: Lazy propagation and slicing (compressing search space) ideas in segment tree.
#1: Finding number of intersecting points among axis parallel line segments.
#2: Perimeter and area of union of rectangles.
#3: Finding points in number of rectangles and rectangles covering points.
#4: Sliding window ideas, finding maximal number of points covered by a rectangle placed arbitrarily.
-- and a few others.
After the discussion, we solved this problem to test if we were able to learn anything at all.
Hopefully, the next class, we will have a discussion on the problems on APIO:2007
Problems to be solved before the next class:
All are from http://www.spoj.pl/
Edit: A virtual contest has been arranged. Visit this link.