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An Eulerian trail, [note 1] or Euler walk, in an undirected graph is a walk that uses each edge exactly once. If such a walk exists, the graph is called traversable or semi-eulerian. [3] An Eulerian cycle, [note 1] also called an Eulerian circuit or Euler tour, in an undirected graph is a cycle that uses each edge exactly once.
A directed walk is a finite or infinite sequence of edges directed in the same direction which joins a sequence of vertices. [2]Let G = (V, E, ϕ) be a directed graph. A finite directed walk is a sequence of edges (e 1, e 2, …, e n − 1) for which there is a sequence of vertices (v 1, v 2, …, v n) such that ϕ(e i) = (v i, v i + 1) for i = 1, 2, …, n − 1.
2. A closed walk is one that starts and ends at the same vertex; see walk. 3. A graph is transitively closed if it equals its own transitive closure; see transitive. 4. A graph property is closed under some operation on graphs if, whenever the argument or arguments to the operation have the property, then so does the result.
A graph with edges colored to illustrate a closed walk, H–A–B–A–H, in green; a circuit which is a closed walk in which all edges are distinct, B–D–E–F–D–C–B, in blue; and a cycle which is a closed walk in which all vertices are distinct, H–D–G–H, in red.
Take a graph G and let M and M ′ be two matchings in G. Let G ′ be the resultant graph from taking the symmetric difference of M and M ′; i.e. (M - M ′) ∪ (M ′ - M). G ′ will consist of connected components that are one of the following: An isolated vertex. An even cycle whose edges alternate between M and M ′.
A graph that contains a Hamiltonian path is called a traceable graph. A graph is Hamiltonian-connected if for every pair of vertices there is a Hamiltonian path between the two vertices. A Hamiltonian cycle , Hamiltonian circuit , vertex tour or graph cycle is a cycle that visits each vertex exactly once.
a forest F in G is an alternating forest with respect to M, if its connected components are alternating trees, and; every exposed vertex in G is a root of an alternating tree in F. Each iteration of the loop starting at line B09 either adds to a tree T in F (line B10) or finds an augmenting path (line B17) or finds a blossom (line B20).
In graph theory and theoretical computer science, the longest path problem is the problem of finding a simple path of maximum length in a given graph.A path is called simple if it does not have any repeated vertices; the length of a path may either be measured by its number of edges, or (in weighted graphs) by the sum of the weights of its edges.