29 November 2004:

Topological sort:
  add the vertex to the beginning of list *after* you visit all its 
  neighbors.

Dijkstra's algorithm:
  shortest paths problem in a weighted digraph
  (how do you represent a weighted graph?)
  single-pair versus single-source
  start with initial vertex
  need "parents", "distances", and "colors"
    parents -- we build a vector indicating which node preceds it
      in the shortest path.
    distances -- we keep track of the current shortest path to
      each node as it's found.  Initially, each distance is set
      to "infinity" except for the start node (which is 0)
    colors -- indicating whether we've searched a nodes neighbors
      or not
  Algorithm:
   - find white node u with smallest distance to the source (initially, 
     this is the source)
   - color u black
   - for each of u's neighbors v:
     - let new-dist be distance[u] + weight(u,v)
     - if new-dist <= distance[v]:
       - set parent[v] to be u
       - set distance[v] to be new-dist
   - repeat until all nodes are black

  Then, we can construct the shortest path from any node to u by
  tracing through the "parent" array.  We reverse the path to get
  the shortest path from u to that node.

  Run time: O(E V^2)
  Can do O(E log(V)) -- how?