In graph theory, a biconnected graph is a connected and "nonseparable" graph, meaning that if any one vertex were to be removed, the graph will remain connected. Therefore a biconnected graph has no articulation vertices.
The property of being 2-connected is equivalent to biconnectivity, except that the complete graph of two vertices is usually not regarded as 2-connected.
This property is especially useful in maintaining a graph with a two-fold redundancy, to prevent disconnection upon the removal of a single edge (or connection).
The use of biconnected graphs is very important in the field of networking (see Network flow), because of this property of redundancy.
Definition
editA biconnected undirected graph is a connected graph that is not broken into disconnected pieces by deleting any single vertex (and its incident edges).
A biconnected directed graph is one such that for any two vertices v and w there are two directed paths from v to w which have no vertices in common other than v and w.
Examples
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A biconnected graph on four vertices and four edges
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A graph that is not biconnected. The removal of vertex x would disconnect the graph.
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A biconnected graph on five vertices and six edges
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A graph that is not biconnected. The removal of vertex x would disconnect the graph.
| Vertices | Number of Possibilities |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 1 |
| 4 | 3 |
| 5 | 10 |
| 6 | 56 |
| 7 | 468 |
| 8 | 7123 |
| 9 | 194066 |
| 10 | 9743542 |
| 11 | 900969091 |
| 12 | 153620333545 |
| 13 | 48432939150704 |
| 14 | 28361824488394169 |
| 15 | 30995890806033380784 |
| 16 | 63501635429109597504951 |
| 17 | 244852079292073376010411280 |
| 18 | 1783160594069429925952824734641 |
| 19 | 24603887051350945867492816663958981 |
Structure of 2-connected graphs
editEvery 2-connected graph can be constructed inductively by adding paths to a cycle (Diestel 2016, p. 59).
See also
editReferences
edit- Eric W. Weisstein. "Biconnected Graph." From MathWorld—A Wolfram Web Resource. http://mathworld.wolfram.com/BiconnectedGraph.html
- Paul E. Black, "biconnected graph", in Dictionary of Algorithms and Data Structures [online], Paul E. Black, ed., U.S. National Institute of Standards and Technology. 17 December 2004. (accessed TODAY) Available from: https://xlinux.nist.gov/dads/HTML/biconnectedGraph.html
- Diestel, Reinhard (2016), Graph Theory (5th ed.), Berlin, New York: Springer-Verlag, ISBN 978-3-662-53621-6.
External links
edit- The tree of the biconnected components Java implementation in the jBPT library (see BCTree class).