Exact Algorithms for L(2,1)-Labeling of Graphs

Abstract : The notion of distance constrained graph labelings, motivated by the Frequency Assignment Problem, reads as follows: A mapping from the vertex set of a graph $G=(V,E)$ into an interval of integers $\{0, \dots ,k\}$ is an $L(2,1)$-labeling of $G$ of span $k$ if any two adjacent vertices are mapped onto integers that are at least 2 apart, and every two vertices with a common neighbor are mapped onto distinct integers. It is known that for any fixed $k\ge 4$, deciding the existence of such a labeling is an NP-complete problem. We present exact exponential time algorithms that are faster than the naive $O^*((k+1)^n)$ algorithm that would try all possible mappings. The improvement is best seen in the first NP-complete case of $k=4$, where the running time of our algorithm is $O(1.3006^n)$. Furthermore we show that dynamic programming can be used to establish an $O(3.8730^n)$ algorithm to compute an optimal $L(2,1)$-labeling.
Type de document :
Article dans une revue
Algorithmica, Springer Verlag, 2011, 59 (2), pp.169-194. <10.1007/s00453-009-9302-7>
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Contributeur : Mathieu Liedloff <>
Soumis le : mardi 2 mars 2010 - 16:44:32
Dernière modification le : mardi 13 décembre 2016 - 15:44:54



Frédéric Havet, Martin Klazar, Jan Kratochvil, Dieter Kratsch, Mathieu Liedloff. Exact Algorithms for L(2,1)-Labeling of Graphs. Algorithmica, Springer Verlag, 2011, 59 (2), pp.169-194. <10.1007/s00453-009-9302-7>. <hal-00460873>



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