Essential things to remember from today's class (class 17, 23rd October)

Be sure to understand and be able to recreate for a similar problem the
   "brute force" (just try every combination) solution for the knapsack
   problem.
   
And be sure you understand why its time is exponential, and just how bad
   that is.
   
Be sure you understand and could recreate the dynamic programming solution
   to the combinatoric C(n, r) problem.

And the same for the "how many shortest paths in a grid?" problem.