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In graph theory, a line perfect graph is a graph whose line graph is a perfect graph. Equivalently, these are the graphs in which every odd-length simple cycle is a triangle. A graph is line perfect if and only if each of its biconnected components is a
bipartite graph In the mathematical field of graph theory, a bipartite graph (or bigraph) is a graph whose vertices can be divided into two disjoint and independent sets U and V, that is every edge connects a vertex in U to one in V. Vertex sets U and V are ...
, the complete graph , or a triangular book . Because these three types of biconnected component are all perfect graphs themselves, every line perfect graph is itself perfect. By similar reasoning, every line perfect graph is a parity graph, a Meyniel graph, and a perfectly orderable graph. Line perfect graphs generalize the bipartite graphs, and share with them the properties that the maximum matching and
minimum vertex cover In graph theory, a vertex cover (sometimes node cover) of a graph is a set of vertices that includes at least one endpoint of every edge of the graph. In computer science, the problem of finding a minimum vertex cover is a classical optimizat ...
have the same size, and that the chromatic index equals the
maximum degree This is a glossary of graph theory. Graph theory is the study of graphs, systems of nodes or vertices connected in pairs by lines or edges. Symbols A B ...
.


See also

* Strangulated graph, a graph in which every
peripheral cycle In graph theory, a peripheral cycle (or peripheral circuit) in an undirected graph is, intuitively, a cycle that does not separate any part of the graph from any other part. Peripheral cycles (or, as they were initially called, peripheral polygo ...
is a triangle


References

{{reflist, refs= {{citation , last = de Werra , first = D. , doi = 10.1007/BF01609025 , issue = 2 , journal = Mathematical Programming , mr = 509968 , pages = 236–238 , title = On line-perfect graphs , volume = 15 , year = 1978. {{citation , last1 = Grötschel , first1 = Martin , author1-link = Martin Grötschel , last2 = Lovász , first2 = László , author2-link = László Lovász , last3 = Schrijver , first3 = Alexander , author3-link = Alexander Schrijver , doi = 10.1007/978-3-642-78240-4 , edition = 2nd , isbn = 3-540-56740-2 , mr = 1261419 , page = 281 , publisher = Springer-Verlag, Berlin , series = Algorithms and Combinatorics , title = Geometric algorithms and combinatorial optimization , url = https://books.google.com/books?id=hWvmCAAAQBAJ&pg=PA281 , volume = 2 , year = 1993. {{citation , last = Maffray , first = Frédéric , doi = 10.1016/0095-8956(92)90028-V , issue = 1 , journal =
Journal of Combinatorial Theory The ''Journal of Combinatorial Theory'', Series A and Series B, are mathematical journals specializing in combinatorics and related areas. They are published by Elsevier. ''Series A'' is concerned primarily with structures, designs, and applicat ...
, mr = 1159851 , pages = 1–8 , series = Series B , title = Kernels in perfect line-graphs , volume = 55 , year = 1992, doi-access = free .
{{citation , last = Trotter , first = L. E., Jr. , doi = 10.1007/BF01593791 , issue = 2 , journal = Mathematical Programming , mr = 0457293 , pages = 255–259 , title = Line perfect graphs , volume = 12 , year = 1977 {{citation , last = Wagler , first = Annegret , contribution = Critical and anticritical edges in perfect graphs , doi = 10.1007/3-540-45477-2_29 , mr = 1905643 , pages = 317–327 , publisher = Springer , location = Berlin , series = Lecture Notes in Computer Science , title = Graph-Theoretic Concepts in Computer Science: 27th International Workshop, WG 2001, Boltenhagen, Germany, June 14–16, 2001, Proceedings , volume = 2204 , year = 2001. Perfect graphs