Generating graceful unicyclic graphs from a given forest

Abstract

Acharya (1982) proved that every connected graph can be embedded in a graceful graph. The generalization of this result that, any set of graphs can be packed into a graceful graph was proved by Sethuraman and Elumalai (2005). Recently, Sethuraman et al. (2016) have shown that, every tree can be embedded in an graceful tree. Inspired by these fundamental structural properties of graceful graphs, in this paper, we prove that any acyclic graph can be embedded in an unicyclic graceful graph. This result is proved algorithmically by constructing graceful unicyclic graphs from a given acyclic graph. Our result strongly supports the Truszczynski’s Conjecture that “All unicyclic graphs except the cycle with or 2(mod 4) are graceful”.

Keywords

• graceful tree
• graceful unicyclic graph
• graceful tree embedding
• graceful labeling
• graph labeling