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» Schaefer's theorem for graphs
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JCO
2006
128views more  JCO 2006»
14 years 11 months ago
A combinatorial theorem on labeling squares with points and its application
In this paper, we present a combinatorial theorem on labeling disjoint axis-parallel squares of edge length two using points. Given an arbitrary set of disjoint axis-parallel squar...
Binhai Zhu, Minghui Jiang
83
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CP
2008
Springer
15 years 1 months ago
Perfect Constraints Are Tractable
By using recent results from graph theory, including the Strong Perfect Graph Theorem, we obtain a unifying framework for a number of tractable classes of constraint problems. Thes...
András Z. Salamon, Peter G. Jeavons
COMBINATORICS
2006
155views more  COMBINATORICS 2006»
14 years 11 months ago
Orthogonal Art Galleries with Holes: A Coloring Proof of Aggarwal's Theorem
We prove that n+h 4 vertex guards are always sufficient to see the entire interior of an n-vertex orthogonal polygon P with an arbitrary number h of holes provided that there exis...
Pawel Zylinski
JGT
2007
85views more  JGT 2007»
14 years 11 months ago
Coloring quasi-line graphs
A graph G is a quasi-line graph if for every vertex v, the set of neighbors of v can be expressed as the union of two cliques. The class of quasi-line graphs is a proper superset ...
Maria Chudnovsky, Alexandra Ovetsky
IPCO
1998
125views Optimization» more  IPCO 1998»
15 years 1 months ago
A Characterization of Weakly Bipartite Graphs
We give a proof of Guenin's theorem characterizing weakly bipartite graphs by not having an odd-K5 minor. The proof curtails the technical and case-checking parts of Guenin�...
Bertrand Guenin