Results 211 to 220 of about 6,300 (231)

The Complexity of Coloring Circular Arcs and Chords

SIAM Journal on Algebraic and Discrete Methods, 1980
The word problem for products of symmetric groups, the circular arc graph coloring problem, and the circle graph coloring problem, as well as several related problems, are proved to be $NP$-complete. For any fixed number K of colors, the problem of determining whether a given circular arc graph is K-colorable is shown to be solvable in polynomial time.
M R Garey, C H Papadimitriou, D S Johnson   +2 more
exaly   +3 more sources

Circular Coloring of Planar Digraphs

Graphs and Combinatorics, 2011
zbMATH Open Web Interface contents unavailable due to conflicting licenses.
Guanghui Wang 0002, Bin Liu 0009, Jiguo Yu, Guizhen Liu   +3 more
openaire   +1 more source

Circular colorings of weighted graphs

Journal of Graph Theory, 1996
zbMATH Open Web Interface contents unavailable due to conflicting licenses.
Walter A. Deuber, Xuding Zhu
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Acyclic Homomorphisms and Circular Colorings of Digraphs

SIAM Journal on Discrete Mathematics, 2003
An acyclic homomorphism of a digraph \(D\) into a digraph \(F\) is a mapping \(\phi: V(D) \to V(F)\) such that (i) for every arc \(uv \in E(D)\), either \(\phi(u)=\phi(v)\) or \(\phi(u)\phi(v)\) is an arc of \(F\) and (ii) for every vertex \(v\in V(F)\), the subgraph of \(D\) induced by \(\phi^{-1}(v)\) is acyclic.
Tomás Feder, Pavol Hell, Bojan Mohar
openaire   +1 more source

Defective circular coloring [PDF]

Australas. J Comb., 2002
A defective circular coloring for a simple graph \(G= (V,E)\) is a function \(c: V\to \{0,1,\dots, k-1\}\) such that each vertex \(v\) is adjacent to at most \(d\) vertices \(u\) not satisfying \(q\leq|c(v)- c(u)|\leq k-q\). If such a defective circular coloring exists, then \(G\) is said to be \((k/q, d)\)-colorable.
openaire   +1 more source

Circular histogram thresholding for color image segmentation

Proceedings of 3rd International Conference on Document Analysis and Recognition, 2002
A circular histogram thresholding for color image segmentation is proposed. A circular hue histogram is first constructed based on a UCS (I,H,S) color space. The histogram is automatically smoothed by a scale-space filter, then transformed into traditional histogram form, and finally recursively thresholded based on the maximum principle of variance ...
Din-Chang Tseng, Yao-Fu Li, Cheng-Tan Tung   +2 more
openaire   +1 more source

Circular list colorings of some graphs

Journal of Applied Mathematics and Computing, 2006
Combining the notions of circular colorings [see \textit{X. Zhu}, Discrete Math. 229, 371--410 (2001; Zbl 0973.05030)] and of list colorings [see \textit{N. Alon} and \textit{M. Tarsi}, Combinatorica 12, 125--134 (1992; Zbl 0756.05049)] in an obvious way the authors introduce circular list colorings of graphs.
Wang, Guanghui, Liu, Guizhen, Yu, Jiguo
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Coloring Circular Arcs with Applications.

2000
The circular arc coloring problem is the problem of finding a minimal coloring of a set of arcs on a circle so that if two arcs intersect then they are assigned different colors. When a generic set of circular arcs is to be colored, the problem is known to be NP-complete; we consider certain instances of the problem which can be optimally solved in ...
GARGANO, Luisa, RESCIGNO, Adele Anna
openaire   +1 more source

Circular coloring and fractional coloring in planar graphs

Journal of Graph Theory, 2022
Xiaolan Hu, Jiaao Li
exaly  

Circular \({\boldsymbol{(4-\epsilon )}}\) -Coloring of Some Classes of Signed Graphs

SIAM Journal on Discrete Mathematics, 2023
Reza Naserasr, Jonathan Narboni
exaly