2.6.1 DAGs Video
PROFESSOR: Directed acyclic graphs are a special class of graphs that really have and warrant a theory of their own. Of course, "directed acyclic graphs" is lot of syllables, so they're called "DAGs" for short. OK. So here's why they come up all the time. Let's look at a diagram that may be familiar to you. This shows the prerequisite structure of required courses in the 6-3 program of MIT Electrical Engineering and Computer Science department. There are similar charts for the other sub-majors of EECS and in other departments as well. So what does it mean? Well, let's look at this vertex corresponding to the first term calculus class 18.01. And there's an edge that points to 6.042. And that's because, if you look at the catalogue, 6.042 lists 18.01 as a prerequisite. If you look at the algorithms-- introductory algorithms-- class 6.006, you'll find, if you look in the catalog, that it has listed two prerequisites, 6.042 and ...