On indicated coloring of some classes of graphs

TL;DR

This paper studies indicated coloring in specific classes of graphs, providing structural characterizations and proving that these classes are k-indicated colorable for all k greater than or equal to their chromatic number.

Contribution

It offers new structural insights and proves k-indicated colorability for certain classes of graphs with forbidden induced subgraphs.

Findings

Structural characterization of certain {P5,K4,Kite,Bull}-free graphs with induced C5.

Proof that specific graph classes are k-indicated colorable for all k ≥ χ(G).

Partial answer to a question by A. Grzesik on indicated coloring.

Abstract

Indicated coloring is a type of game coloring in which two players collectively color the vertices of a graph in the following way. In each round the first player (Ann) selects a vertex, and then the second player (Ben) colors it properly, using a fixed set of colors. The goal of Ann is to achieve a proper coloring of the whole graph, while Ben is trying to prevent the realization of this project. The smallest number of colors necessary for Ann to win the game on a graph $G$ (regardless of Ben's strategy) is called the indicated chromatic number of $G$, denoted by $\chi_i(G)$. In this paper, we obtain structural characterization of connected $\{P_5,K_4,Kite,Bull\}$-free graphs which contains an induced $C_5$ and connected $\{P_6,C_5, K_{1,3}\}$-free graphs that contains an induced $C_6$. Also, we prove that $\{P_5,K_4,Kite,Bull\}$-free graphs that contains an induced $C_5$ and $\{P_6,C_5,\overline{P_5}, K_{1,3}\}$-free graphs which contains an induced $C_6$ are $k$-indicated colorable for all $k\geq\chi(G)$. In addition, we show that $\mathbb{K}[C_5]$ is $k$-indicated colorable for all $k\geq\chi(G)$ and as a consequence, we exhibit that $\{P_2\cup P_3, C_4\}$-free graphs, $\{P_5,C_4\}$-free graphs are $k$-indicated colorable for all $k\geq\chi(G)$. This partially answers one of the questions which was raised by A. Grzesik in \cite{and}.