Labelling graphs with a condition at distance 2
SIAM Journal on Discrete Mathematics
The $L(2,1)$-Labeling Problem on Graphs
SIAM Journal on Discrete Mathematics
Fixed parameter complexity of λ-labelings
Discrete Applied Mathematics - special issue on the 25th international workshop on graph theoretic concepts in computer science (WG'99)
NP-Completeness Results and Efficient Approximations for Radiocoloring in Planar Graphs
MFCS '00 Proceedings of the 25th International Symposium on Mathematical Foundations of Computer Science
The complexity of satisfiability problems
STOC '78 Proceedings of the tenth annual ACM symposium on Theory of computing
L(h,1)-labeling subclasses of planar graphs
Journal of Parallel and Distributed Computing
The L(h, k)-Labelling Problem: A Survey and Annotated Bibliography
The Computer Journal
Radiocoloring in planar graphs: complexity and approximations
Theoretical Computer Science - Mathematical foundations of computer science 2000
Labeling planar graphs with a condition at distance two
European Journal of Combinatorics
Proceedings of the nineteenth annual ACM-SIAM symposium on Discrete algorithms
Coloring the square of a planar graph
Journal of Graph Theory
Complexity of (p,1)-total labelling
Discrete Applied Mathematics
An O(n1.75) algorithm for L(2,1)-labeling of trees
Theoretical Computer Science
Distance constrained labelings of graphs of bounded treewidth
ICALP'05 Proceedings of the 32nd international conference on Automata, Languages and Programming
On the complexity of exact algorithm for L (2, 1)-labeling of graphs
Information Processing Letters
Determining the l(2,1)-span in polynomial space
WG'12 Proceedings of the 38th international conference on Graph-Theoretic Concepts in Computer Science
Determining the L(2,1)-span in polynomial space
Discrete Applied Mathematics
Fast exact algorithm for L(2,1)-labeling of graphs
Theoretical Computer Science
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A mapping from the vertex set of a graph G=(V,E) into an interval of integers {0,...,k} is an L(2,1)-labelling of G of span k if any two adjacent vertices are mapped onto integers that are at least 2 apart, and every two vertices at distance 2 are mapped onto distinct integers. It is known that, for any fixed k=4, deciding the existence of such a labelling is an NP-complete problem while it is polynomial for k@?3. For even k=8, it remains NP-complete when restricted to planar graphs. In this paper, we show that it remains NP-complete for any k=4 by reduction from Planar Cubic Two-Colourable Perfect Matching. Schaefer stated without proof that Planar Cubic Two-Colourable Perfect Matching is NP-complete. In this paper we give a proof of this.