Lecture 17: 10/25/07 . There are 2 typos on the last page -- 0 must
be replaced by i - 1 in the final assignment. Also i ranges from 1 to j
(and not j-1) in the minimization.
Lecture 20: 11/08/07 . This is based on a paper "A simple algorithm for
finding frequent elements in streams and bags" by Karp, Shenker, and
Papadimitriou. Part 2 of this lecture is on topological sort.