1. Lecture 16 CSE 331 Oct 9, 2009

2. Announcements Hand in your HW4 Solutions to HW4 next week Remember next week I will not be here so

3. HW 5 Exercise 3 in Chapter 3 (80 points) Exercise 9 in Chapter 3 (20 points)

4. Reading Assignment Sec 3.3, 3.4 and 3.5 of [KT]

5. Directed graphs Model asymmetric relationships Precedence relationships u needs to be done before v means (u,v) edge

6. Directed graphs Adjacency matrix is not symmetric Each vertex has two lists in Adj. list rep.

7. Directed Acyclic Graph (DAG) No directed cycles Precedence relationships are consistent

8. Topological Ordering of a DAG Order the vertices so that all edges go “forward”

9. Today’s agenda Algorithm to compute topological ordering of a DAG