Chromatic Layout Number of Paths and Cycles

Jasintha Quadras1, Vasanthika S2
1Department of Mathematics, Stella Maris College, Chennai 600 034, India
2School of Advanced Sciences, VIT University, Chennai 600 127, India

Abstract

A linear layout, or simply a layout, of an undirected graph \( G = (V, E) \) with \( n = |V| \) vertices is a bijective function \( \phi: V \to \{1, 2, \dots, n\} \). A \( k \)-coloring of a graph \( G = (V, E) \) is a mapping \( \kappa: V \to \{c_1, c_2, \dots, c_k\} \) such that no two adjacent vertices have the same color. A graph with a \( k \)-coloring is called a \( k \)-colored graph.

A colored layout of a \( k \)-colored graph \( (G, \kappa) \) is a layout \( \phi \) of \( G \) such that for any \( u, x, v \in V \), if \( (u, v) \in E \) and \( \phi(u) < \phi(x) < \phi(v) \), then \( \kappa(u) \neq \kappa(x) \). Given a \( k \)-colored graph \( (G, \kappa) \), the problem of deciding whether there is a colored layout \( \phi \) of \( (G, \kappa) \) is NP-complete. In this paper, we introduce the concept of chromatic layout of \( G \) and determine the chromatic layout number for paths and cycles.