spanning
play

Spanning G is a subgraph that has all the vertices of G. Trees - PowerPoint PPT Presentation

SpanningSubgraphs MathematicsforComputerScience MIT6.042J/18.062J A spanning subgraph of graph Spanning G is a subgraph that has all the vertices of G. Trees Albert R Meyer, April 8, 2013 Albert R Meyer, April 8, 2013 spanning.1


  1. Spanning Subgraphs Mathematics for Computer Science MIT 6.042J/18.062J A spanning subgraph of graph Spanning G is a subgraph that has all the vertices of G. Trees Albert R Meyer, April 8, 2013 Albert R Meyer, April 8, 2013 spanning.1 spanning.2 Spanning Subgraphs Spanning Trees A spanning subgraph of graph G is a subgraph that has all the vertices of G. A spanning tree is a spanning subgraph that is a tree. Albert R Meyer, April 8, 2013 Albert R Meyer, April 8, 2013 spanning.3 spanning.4 1

  2. Spanning Trees Spanning Trees another spanning tree a spanning tree (can have many) Albert R Meyer, April 8, 2013 Albert R Meyer, April 8, 2013 spanning.5 spanning.6 Spanning Trees Minimum Weight Spanning Trees Suppose edges have weights: Lemma: G connected implies 3 G has a spanning tree 4 1 4 Pf: Namely, any minimum edge 9 7 2 6 connected spanning graph. 1 Find min weight spanning tree? Albert R Meyer, April 8, 2013 Albert R Meyer, April 8, 2013 spanning.7 min-tree.9 2

  3. Build MST using gray edges Minimum Spanning Trees color components • Start with vertices • Color components black & white 3 4 4 1 • gray edge ::= 9 7 2 • add min weight gray edge 6 1 Albert R Meyer, April 8, 2013 Albert R Meyer, April 8, 2013 min-tree.10 min-tree.11 Minimum Spanning Trees Minimum Spanning Trees color components gray edges 3 3 4 4 1 1 4 4 9 9 7 7 2 2 6 6 1 1 Albert R Meyer, April 8, 2013 Albert R Meyer, April 8, 2013 min-tree.12 min-tree.13 3

  4. Minimum Spanning Trees Minimum Spanning Trees gray edges: min weight re-color components 3 3 4 4 4 1 4 1 9 9 7 7 2 2 6 6 1 1 Albert R Meyer, April 8, 2013 Albert R Meyer, April 8, 2013 min-tree.14 min-tree.15 Minimum Spanning Trees Minimum Spanning Trees re-color components gray edges 3 3 4 4 1 1 4 4 9 9 7 7 2 2 6 6 1 1 Albert R Meyer, April 8, 2013 Albert R Meyer, April 8, 2013 min-tree.16 min-tree.17 4

  5. Minimum Spanning Trees Minimum Spanning Trees gray edges: min weight re-color components 3 3 4 4 4 1 4 1 9 9 7 7 2 2 6 6 1 1 Albert R Meyer, April 8, 2013 Albert R Meyer, April 8, 2013 min-tree.18 min-tree.19 Minimum Spanning Trees Minimum Spanning Trees re-color components etc 3 3 4 4 1 1 4 4 9 9 7 7 2 2 6 6 1 1 Albert R Meyer, April 8, 2013 Albert R Meyer, April 8, 2013 min-tree.20 min-tree.21 5

  6. Ways to grow an MST • start at any vertex, keep building one tree. (Prim) • keep choosing min weight edge between diff components (Kruskal) • grow trees in parallel (Meyer) Albert R Meyer, April 8, 2013 min-tree.22 6

  7. MIT OpenCourseWare http://ocw.mit.edu 6.042J / 18.062J Mathematics for Computer Science Spring 20 15 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms.

Download Presentation
Download Policy: The content available on the website is offered to you 'AS IS' for your personal information and use only. It cannot be commercialized, licensed, or distributed on other websites without prior consent from the author. To download a presentation, simply click this link. If you encounter any difficulties during the download process, it's possible that the publisher has removed the file from their server.

Recommend


More recommend