Exemple de utilizare a Bipartite graphs în Engleză și traducerile lor în Română
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Isomorphic bipartite graphs have the same degree sequence.
In particular- d is an eigenvalue of bipartite graphs.
Bipartite graphs may be characterized in several different ways.
Isaev(2009)."Asymptotic number of Eulerian circuits in complete bipartite graphs".
The 2-colorable graphs are exactly the bipartite graphs, including trees and forests.
The charts numismatists produce to represent the production of coins are bipartite graphs.
Bipartite graphs are extensively used in modern coding theory, especially to decode codewords received from the channel.
When modelling relations between two different classes of objects, bipartite graphs very often arise naturally.
The bipartite graphs, line graphs of bipartite graphs, and their complements form four out of the five basic classes of perfect graphs used in the proof of the strong perfect graph theorem.[20].
Biadjacency matrices may be used to describe equivalences between bipartite graphs, hypergraphs, and directed graphs. .
Perfection of bipartite graphs is easy to see(their chromatic number is two and their maximum clique size is also two) but perfection of the complements of bipartite graphs is less trivial, and is another restatement of König's theorem.
The Dulmage- Mendelsohn decomposition is a structural decomposition of bipartite graphs that is useful in finding maximum matchings.[36].
It can be shown that for each eigenvalue λ i{\displaystyle\lambda_{i}}, its opposite- λ i= λ n+ 1- i{\displaystyle-\lambda_{i}=\lambda_{n+1-i}} is also an eigenvalue of A if G is a bipartite graph.In particular- d is an eigenvalue of bipartite graphs.
Under this correspondence,the biadjacency matrices of bipartite graphs are exactly the incidence matrices of the corresponding hypergraphs.
However, the degree sequence does not, in general, uniquely identify a bipartite graph; in some cases, non-isomorphic bipartite graphs may have the same degree sequence.
In bipartite graphs, the size of minimum vertex cover is equal to the size of the maximum matching; this is König's theorem.[16][17] An alternative and equivalent form of this theorem is that the size of the maximum independent set plus the size of the maximum matching is equal to the number of vertices.
Using this method, he showed how to solve the Hamiltonian cycle problem in arbitrary n-vertex graphs by a Monte Carlo algorithm in time O(1.657n); for bipartite graphs this algorithm can be further improved to time o(1.415n).[7].
Another example where bipartite graphs appear naturally is in the(NP-complete) railway optimization problem, in which the input is a schedule of trains and their stops, and the goal is to find a set of train stations as small as possible such that every train visits at least one of the chosen stations.
A similar reinterpretation of adjacency matrices may be used to show a one-to-one correspondence between directed graphs(on a given number of labeled vertices, allowing self-loops)and balanced bipartite graphs, with the same number of vertices on both sides of the bipartition.
Bipartite graphs,[11] undirected planar graphs of maximum degree three,[12] directed planar graphs with indegree and outdegree at most two,[13] bridgeless undirected planar 3-regular bipartite graphs, 3-connected 3-regular bipartite graphs,[14] subgraphs of the square grid graph,[15] cubic subgraphs of the square grid graph.[16].
According to the strong perfect graph theorem,the perfect graphs have a forbidden graph characterization resembling that of bipartite graphs: a graph is bipartite if and only if it has no odd cycle as a subgraph, and a graph is perfect if and only if it has no odd cycle or its complement as an induced subgraph.
The biadjacency matrix of a bipartite graph( U, V, E){\displaystyle(U, V, E)} is a(0,1)-matrix of size| U|×| V|{\displaystyle|U|\times|V|} that has a one for each pair of adjacent vertices and a zero for nonadjacent vertices.[21] Biadjacency matrices may be used to describe equivalences between bipartite graphs, hypergraphs, and directed graphs. .
As a special case of this correspondence between bipartite graphs and hypergraphs, any multigraph(a graph in which there may be two or more edges between the same two vertices) may be interpreted as a hypergraph in which some hyperedges have equal sets of endpoints, and represented by a bipartite graph that does not have multiple adjacencies and in which the vertices on one side of the bipartition all have degree two.[22].
This situation can be modeled as a bipartite graph( P, J, E){\displaystyle(P, J, E)} where an edge connects each job-seeker with each suitable job.[34] A perfect matching describes a way of simultaneously satisfying all job-seekers and filling all jobs;Hall's marriage theorem provides a characterization of the bipartite graphs which allow perfect matchings.
In any graph without isolated vertices the size of the minimum edge cover plus the size of a maximum matching equals the number of vertices.[18]Combining this equality with König's theorem leads to the facts that, in bipartite graphs, the size of the minimum edge cover is equal to the size of the maximum independent set, and the size of the minimum edge cover plus the size of the minimum vertex cover is equal to the number of vertices.
For perfect graphs, it is possible to find a maximum clique in polynomial time, using an algorithm based on semidefinite programming.[44] However, this method is complex and non-combinatorial, and specialized clique-finding algorithms have been developed for many subclasses of perfect graphs.[45]In the complement graphs of bipartite graphs, König's theorem allows the maximum clique problem to be solved using techniques for matching.
Polynomial time algorithms are known for many algorithmic problems on matchings, including maximum matching( finding a matching that uses as many edges as possible), maximum weight matching, and stable marriage.[ 31] In many cases,matching problems are simpler to solve on bipartite graphs than on non-bipartite graphs,[ 32] and many matching algorithms such as the Hopcroft- Karp algorithm for maximum cardinality matching[ 33] work correctly only on bipartite inputs.
Bipartite graph, a graph without odd cycles.
The degree sum formula for a bipartite graph states that.
In projective geometry,Levi graphs are a form of bipartite graph used to model the incidences between points and lines in a configuration.