Примери коришћења Planar graphs на Енглеском и њихови преводи на Српски
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Consequently, only planar graphs have duals.
By 1967, Kasteleyn had generalized this result to all planar graphs.
For planar graphs with maximum degree Δ≥ 7, the optimal number of colors is again exactly Δ.
Counting the number of matchings,even for planar graphs, is also P-complete.
For planar graphs with maximum degree Δ≥ 7, the optimal number of colors is again exactly Δ.
Vertex cover remains NP-complete even in cubic graphs and even in planar graphs of degree at most 3.
On the other hand, there exist planar graphs of maximum degree ranging from two through five that are of class two.
The first results about graph coloring deal almost exclusively with planar graphs in the form of the coloring of maps.
Planar graphs were first studied by Ringel(1965), who showed that they can be colored with at most seven colors.
This is proved by a simple induction on the number of vertices which is exactly like the proof of the six-color theorem for planar graphs.
High-degree planar graphs, the number of colors is always Δ, and for multigraphs, the number of colors may be as large as 3Δ/2.
Determining whether a graph can be colored with 2 colors is in P, but with 3 colors is NP-complete,even when restricted to planar graphs.
Vizing(1965) proved that planar graphs of maximum degree at least eight are of class one and conjectured that the same is true for planar graphs of maximum degree seven or six.
Determining whether a graph can be colored with 2 colors is in P, but with 3 colors is NP-complete,even when restricted to planar graphs.
For some graphs, such as bipartite graphs and high-degree planar graphs, the number of colors is always Δ, and for multigraphs, the number of colors may be as large as 3Δ/2.
Planarity testing algorithms typically take advantage of theorems in graph theory that characterize the set of planar graphs in terms that are independent of graph drawings.
In planar graphs, and more generally in families of graphs closed under graph minor operations, it can be made to run in linear time, by removing all but the cheapest edge between each pair of components after each stage of the algorithm.
Garey and Johnson showed shortly afterwards in 1974 that the directed Hamiltonian cycle problem remains NP-complete for planar graphs and the undirected Hamiltonian cycle problem remains NP-complete for cubic planar graphs.
Trying to find all non isomorphic projections of alternating knots andlinks with n crossings, we need to find all non isomorphic 4-regular planar graphs with n vertices and vice versa Among them, we can distinguish graphs with or without digons.
Borůvka 's algorithm can be shown to take O( log V) iterations of the outer loop until it terminates, and therefore to run in time O( E log V), where E is the number of edges, andV is the number of vertices in G. In planar graphs, and more generally in families of graphs closed under graph minor operations, it can be made to run in linear time, by removing all but the cheapest edge between each pair of components after each stage of the algorithm.
Every finite planar graph has a vertex of degree five or less;
For instance, the 16-vertex planar graph shown in the illustration has m= 24 edges.
This result is considered the first theorem of graph theory,specifically of“planar graph theory”.
A conjecture of Fiorini and Wilson that every triangle-free planar graph, other than the claw K1,3, is not uniquely 3-edge-colorable.
Therefore, every planar graph is 5-degenerate, and the degeneracy of any planar graph is at most five.
As any planar graph has arboricity three, the thickness of any graph is at least equal to a third of the arboricity, and at most equal to the arboricity.
However, the same result also implies that every planar graph of bounded degree has a balanced cut with O(√n) edges.
This 3-regular planar graph has 16 vertices and 24 edges, but only 7 edges in any maximum matching.
Every finite planar graph has a vertex of degree five orless; therefore, every planar graph is 5-degenerate, and the degeneracy of any planar graph is at most five.
This solution is considered to be the first theorem of graph theory,specifically of planar graph theory.