Colouring $(P_r+P_s)$-Free Graphs

Fuente: arXiv
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Autores principales: Klimošová, Tereza, Malík, Josef, Masařík, Tomáš, Novotná, Jana, Paulusma, Daniël, Slívová, Veronika
Formato: Preprint
Publicado: 2018
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author Klimošová, Tereza
Malík, Josef
Masařík, Tomáš
Novotná, Jana
Paulusma, Daniël
Slívová, Veronika
author_facet Klimošová, Tereza
Malík, Josef
Masařík, Tomáš
Novotná, Jana
Paulusma, Daniël
Slívová, Veronika
contents The $k$-Colouring problem is to decide if the vertices of a graph can be coloured with at most $k$ colours for a fixed integer $k$ such that no two adjacent vertices are coloured alike. If each vertex u must be assigned a colour from a prescribed list $L(u) \subseteq \{1,\cdots, k\}$, then we obtain the List $k$-Colouring problem. A graph $G$ is $H$-free if $G$ does not contain $H$ as an induced subgraph. We continue an extensive study into the complexity of these two problems for $H$-free graphs. The graph $P_r+P_s$ is the disjoint union of the $r$-vertex path $P_r$ and the $s$-vertex path $P_s$. We prove that List $3$-Colouring is polynomial-time solvable for $(P_2+P_5)$-free graphs and for $(P_3+P_4)$-free graphs. Combining our results with known results yields complete complexity classifications of $3$-Colouring and List $3$-Colouring on $H$-free graphs for all graphs $H$ up to seven vertices.
format Preprint
id arxiv_https___arxiv_org_abs_1804_11091
institution arXiv
publishDate 2018
record_format arxiv
spellingShingle Colouring $(P_r+P_s)$-Free Graphs
Klimošová, Tereza
Malík, Josef
Masařík, Tomáš
Novotná, Jana
Paulusma, Daniël
Slívová, Veronika
Data Structures and Algorithms
Computational Complexity
The $k$-Colouring problem is to decide if the vertices of a graph can be coloured with at most $k$ colours for a fixed integer $k$ such that no two adjacent vertices are coloured alike. If each vertex u must be assigned a colour from a prescribed list $L(u) \subseteq \{1,\cdots, k\}$, then we obtain the List $k$-Colouring problem. A graph $G$ is $H$-free if $G$ does not contain $H$ as an induced subgraph. We continue an extensive study into the complexity of these two problems for $H$-free graphs. The graph $P_r+P_s$ is the disjoint union of the $r$-vertex path $P_r$ and the $s$-vertex path $P_s$. We prove that List $3$-Colouring is polynomial-time solvable for $(P_2+P_5)$-free graphs and for $(P_3+P_4)$-free graphs. Combining our results with known results yields complete complexity classifications of $3$-Colouring and List $3$-Colouring on $H$-free graphs for all graphs $H$ up to seven vertices.
title Colouring $(P_r+P_s)$-Free Graphs
topic Data Structures and Algorithms
Computational Complexity
url https://arxiv.org/abs/1804.11091