Nicely graceful labellings of tadpoles

Document Type : Original paper

Authors

1 Department of Mathematics, Universitas Pendidikan Ganesha, Bali, Indonesia

2 Department of Applied Mathematics and Informatics, Technical University of Koˇsice, Slovak

3 Department of Mathematical Science, RMIT University, Melbourne, Australia

4 Department of Applied Mathematics and Informatics, Technical University of Košice, Slovak

5 Department of Informatics, Universitas Pendidikan Ganesha, Bali, Indonesia

Abstract

A vertex-labelling $f:V\to \{0,1,\ldots, |E|\}$  for a finite undirected simple graph $G(V, E)$ is called graceful  if $f$ is injective and satisfies the additional property that $\{|f(u)-f(v)|: \text{for every edge} uv\in E\}=\{1,2,\ldots,|E|\}$, where $|E|$ is the number of edges in $G$. Let $M$ be a maximum matching in $G$ and let $f$ also satisfy the property that $f(u)+f(v)=W$ for every $uv\in M$, where $W$ is a constant; then the labelling $f$ is called nicely graceful.  Furthermore,  if  $M$ is a perfect matching in $G$, then $f$ is said to be strongly graceful. In this paper, we investigate nicely and strongly graceful labellings of cycles and tadpoles that are obtained from a cycle by attaching a path to a vertex of the cycle. This leads to a complete characterisation of nicely graceful cycles and strongly graceful tadpoles.

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