Examples of using Ear decomposition in English and their translations into Russian
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If G is 2-vertex-connected,C is an open ear decomposition.
The concept of an ear decomposition can be extended from graphs to matroids.
Then A directed graph is biconnected if andonly if it has an open ear decomposition.
An ear decomposition is odd if each of its ears uses an odd number of edges.
Several important classes of graphs may be characterized as the graphs having certain types of ear decompositions.
Ear decompositions may be used to characterize several important graph classes, and as part of efficient graph algorithms.
Alternatively, efficient sequential andparallel algorithms may be based on ear decomposition.
See in particular Theorems 18(relating ear decomposition to circuit rank) and 19 on the existence of ear decompositions. .
The graphs for which these bounds are tight may be characterized by having odd ear decompositions of a specific form.
An open ear decomposition or a proper ear decomposition is an ear decomposition in which the two endpoints of each ear after the first are distinct from each other.
László Lovász(1972) found that: A graph G is factor-critical if andonly if G has an odd ear decomposition.
Ear decompositions of 2-edge-connected graphs and open ear decompositions of 2-vertex-connected graphs may be found by greedy algorithms that find each ear one at a time.
Then we have the following theorem: A directed graph is strongly connected if andonly if it has an ear decomposition.
Chain decompositions are special ear decompositions depending on a DFS-tree T of G and can be computed very simply: Let every vertex be marked as unvisited.
The following result is due to Herbert Robbins(1939): A graph is 2-edge-connected if andonly if it has an ear decomposition.
Robbins introduced the ear decomposition of 2-edge-connected graphs as a tool for proving the Robbins theorem, that these are exactly the graphs that may be given a strongly connected orientation.
More generally, a result of Frank(1993) makes it possible to find in any graph G the ear decomposition with the fewest even ears. .
A simple greedy approach that computes at the same time ear decompositions, open ear decompositions, st-numberings and-orientations in linear time(if exist) is given in Schmidt 2013a.
The following result is due to Hassler Whitney(1932): A graph G( V, E){\displaystyle G=(V, E)} with| E|≥ 2{\displaystyle|E|\geq 2}is 2-vertex-connected if and only if it has an open ear decomposition.
In any biconnected graph with circuit rank r{\displaystyle r},every open ear decomposition has exactly r{\displaystyle r} ears. .
For instance, to find an ear decomposition of a 2-edge-connected graph, the algorithm of Maon, Schieber& Vishkin(1986) proceeds according to the following steps: Find a spanning tree of the given graph and choose a root for the tree.
Robbins' characterization of the graphs with strong orientations may be proven using ear decomposition, a tool introduced by Robbins for this task.
G is 2-edge-connected if and only if the chains in C partition E. An edge e in G is a bridge if and only if e is not contained in any chain in C. If G is 2-edge-connected,C is an ear decomposition.
In the case that a near-perfect matching of the factor-critical graph is also given, the ear decomposition can be chosen in such a way that each ear alternates between matched and unmatched edges.
An ear decomposition of a given matroid, with the additional constraint that every ear contains the same fixed element of the matroid, may be found in polynomial time given access to an independence oracle for the matroid Coullard& Hellerstein 1996.
Conversely from a sequence of odd cycle contractions, each containing the vertex formed from the previous contraction,one may form an ear decomposition in which the ears are the sets of edges contracted in each step.
A nested ear decomposition is a tree ear decomposition such that, within each ear P j{\displaystyle P_{j}}, the set of pairs of endpoints of other ears P i{\displaystyle P_{i}} that lie within P j{\displaystyle P_{j}} form a set of nested intervals.
Equivalent conditions are that each connected component of the graph has an open ear decomposition, that each connected component is 2-edge-connected, or(by Robbins' theorem) that every connected component has a strong orientation.
An ear decomposition of a matroid is defined to be a sequence of circuits of the matroid, with two properties: each circuit in the sequence has a nonempty intersection with the previous circuits, and each circuit in the sequence remains a circuit even if all previous circuits in the sequence are contracted.
When applied to the graphic matroid of a graph G, this definition of an ear decomposition coincides with the definition of a proper ear decomposition of G: improper decompositions are excluded by the requirement that each circuit include at least one edge that also belongs to previous circuits.