Generally the assignments were really well done.  I think
everybody understand the basic idea behind NP and the
reductions.  The only common error was a misuse of the loop
invariant.

Many people would give loop invariants that are too
vague.  For example, in problem 3, some people have the
correct reduction but the loop in was that G always had a
clique of size k.  They said nothing about the vertices that
have already mean checked and what that means.  In loop
invariants have to be stronger.  G has a clique of size k
and every node that we did not delete is part of every
clique of size k.