Discuss hw11
  (particularly: toss 8 coins; how many ways to get exactly 3 heads)

Graphs:
  def'n (directed);  terminology "vertex/node", "edge"
    example: V={Ian,Vic,AJ,BJ}, with edges ....(drawn)
        (a drawing of a graph is different from a graph;
         also, how algebra's 'graph' relate?  (Distantly.))
  applications of graphs
    scheduling conflicts (assign variables to registers, in a compiler)
    pre-reqs for classes;
    species;
    facebook [which one is my wife?];
    undirected -- how the formal def'n changes

  Representations:
    adjacency-matrix;
    adjacency-list
    (which is better -- running time for looking up relations)
    What does facebook use?
    What about 'adjacency-hash' to solve sparse matrix,
      then keep *both* the list and the hash?

Bjork video about induction.