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Lecture 12

Lecture 12. CSE 331 Sep 25, 2017. Mini Project group due TODAY!. Register for CSE 50!. https://engineering.buffalo.edu/computer-science-engineering/news-events/cse50.html. Use the “Current Student & Faculty Registration” option.

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Lecture 12

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  1. Lecture 12 CSE 331 Sep 25, 2017

  2. Mini Project group due TODAY!

  3. Register for CSE 50! https://engineering.buffalo.edu/computer-science-engineering/news-events/cse50.html Use the “Current Student & Faculty Registration” option We will have class on Friday and HW 3 is still due 11am on Friday

  4. Connectivity Problem Input: Graph G = (V,E) and s in V Output: All t connected to s in G

  5. Breadth First Search (BFS) Build layers of vertices connected to s L0= {s} Assume L0,..,Ljhave been constructed Lj+1set of vertices not chosen yet but are connected to Lj Stop when new layer is empty

  6. BFS Tree BFS naturally defines a tree rooted at s Add non-tree edges Lj forms the jth “level” in the tree u in Lj+1is child of v in Lj from which it was “discovered” L0 1 7 1 9 2 3 L1 2 3 8 0 4 7 8 L2 5 5 4 6 6 L3

  7. Today’s agenda Every edge in is between consecutive layers Computing Connected component

  8. Computing Connected Component Explore(s) Start with R = {s} While exists (u,v) edge v not in R and u in R Add v to R Output R* = R

  9. Questions?

  10. BFS all

  11. Depth First Search (DFS) http://xkcd.com/761/

  12. DFS(u) Mark u as explored and add u to R For each edge (u,v) If v is not explored then DFS(v)

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