1. Lecture 13
CSE 331
Sep 29, 2010

2. Feedback Thanks to everyone who responded
A blog post on the feedback later

3. Homework problems are different
The lectures are not to train you how to solve the HWs/exams
It’s the other way around
If the HW problems seem to come out of the blue, you need to understand
the material better

4. If you’re having troubleUS

5. Grading of Homeworks It will be on the tough side
We want to make sure you learn how to write proofs clearly

6. If you’re not sure why you lost points
the TAs

7. Slow pace of the lectures
A majority finds the pace perfect to a bit fast
Proportion of slow answers is more than expected

8. Puzzles
Feel free to think about them if you are getting bored in class
Come talk to me if you have a solution

9. Puzzle #1 Prove that for the SMP with n men and women
There is no algorithm with running time T(n) such that
Lim n ∞ T(n)/n2 = 0

10. Questions?

11. Graphs
Representation of relationships between pairs of entities/elements
# vertices = n
#edges = m
Edge
Vertex

12. Paths , , Sequence of vertices connected by edges Connected
Path length 3 ,

13. Connected Graphs
Every pair of vertices has a path between them

14. Cycles
Sequence of k vertices connected by edges, first k-1 are distinct ,

16. Tree
Connected undirected graph with no cycles

17. Rooted Tree

18. How many rooted trees can an n vertex tree have?
A rooted tree
How many rooted trees can an n vertex tree have?
AC’s child=SG
Pick any vertex as root
SG’s parent=AC
Let the rest of the tree hang under “gravity”

19. Rest of Today’s agenda
Prove n vertex tree has n-1 edges