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Digraph realization problem. The digraph realization problem is a decision problem in graph theory. Given pairs of nonnegative integers , the problem asks whether there is a labeled simple directed graph such that each vertex has indegree and outdegree .
A drawing of a graph. In mathematics, graph theory is the study of graphs, which are mathematical structures used to model pairwise relations between objects. A graph in this context is made up of vertices (also called nodes or points) which are connected by edges (also called arcs, links or lines ).
Algebraic graph theory is a branch of mathematics in which algebraic methods are applied to problems about graphs. This is in contrast to geometric, combinatoric, or algorithmic approaches. There are three main branches of algebraic graph theory, involving the use of linear algebra, the use of group theory, and the study of graph invariants .
In graph theory, a branch of mathematics, the handshaking lemma is the statement that, in every finite undirected graph, the number of vertices that touch an odd number of edges is even. For example, if there is a party of people who shake hands, the number of people who shake an odd number of other people's hands is even. [ 1]
The Cartesian product of two edges is a cycle on four vertices: K 2 K 2 = C 4. The Cartesian product of K 2 and a path graph is a ladder graph. The Cartesian product of two path graphs is a grid graph. ( K 2 ) n = Q n . {\displaystyle (K_ {2})^ {\square n}=Q_ {n}.} Thus, the Cartesian product of two hypercube graphs is another hypercube: Q i Q ...
Edge cover. In graph theory, an edge cover of a graph is a set of edges such that every vertex of the graph is incident to at least one edge of the set. In computer science, the minimum edge cover problem is the problem of finding an edge cover of minimum size. It is an optimization problem that belongs to the class of covering problems and can ...
The rooted product of graphs. In mathematical graph theory, the rooted product of a graph G and a rooted graph H is defined as follows: take |V ( G) | copies of H, and for every vertex vi of G, identify vi with the root node of the i -th copy of H . More formally, assuming that. and that the root node of H is h1, define. where. and.
Total graph. Tree (graph theory). Trellis (graph) Turán graph. Ultrahomogeneous graph. Vertex-transitive graph. Visibility graph. Museum guard problem. Wheel graph.