On-Line Choice Number of Complete Multipartite Graphs: an Algorithmic Approach

  • Fei-Huang Chang
  • Hong-Bin Chen
  • Jun-Yi Guo
  • Yu-Pei Huang
Keywords: On-line list coloring, Ohba's Conjecture, Paintability


This paper studies the on-line choice number on complete multipartite graphs with independence number $m$. We give a unified strategy for every prescribed $m$. Our main result leads to several interesting consequences comparable to known results. (1) If $k_1-\sum_{p=2}^m\left(\frac{p^2}{2}-\frac{3p}{2}+1\right)k_p\geq 0$, where $k_p$ denotes the number of parts of cardinality $p$, then $G$ is on-line chromatic-choosable. (2) If $|V(G)|\leq\frac{m^2-m+2}{m^2-3m+4}\chi(G)$, then $G$ is on-line chromatic-choosable. (3) The on-line choice number of regular complete multipartite graphs $K_{m\star k}$ is at most
$\left(m+\frac{1}{2}-\sqrt{2m-2}\right)k$ for $m\geq 3$.
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