On almost hypohamiltonian graphs
Discrete mathematics & theoretical computer science, Tome 21 (2019) no. 4
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A graph $G$ is almost hypohamiltonian (a.h.) if $G$ is non-hamiltonian, there exists a vertex $w$ in $G$ such that $G - w$ is non-hamiltonian, and $G - v$ is hamiltonian for every vertex $v \ne w$ in $G$. The second author asked in [J. Graph Theory 79 (2015) 63--81] for all orders for which a.h. graphs exist. Here we solve this problem. To this end, we present a specialised algorithm which generates complete sets of a.h. graphs for various orders. Furthermore, we show that the smallest cubic a.h. graphs have order 26. We provide a lower bound for the order of the smallest planar a.h. graph and improve the upper bound for the order of the smallest planar a.h. graph containing a cubic vertex. We also determine the smallest planar a.h. graphs of girth 5, both in the general and cubic case. Finally, we extend a result of Steffen on snarks and improve two bounds on longest paths and longest cycles in polyhedral graphs due to Jooyandeh, McKay, {\"O}sterg{\aa}rd, Pettersson, and the second author.
@article{DMTCS_2019_21_4_a2,
author = {Goedgebeur, Jan and Zamfirescu, Carol T.},
title = {On almost hypohamiltonian graphs},
journal = {Discrete mathematics & theoretical computer science},
publisher = {mathdoc},
volume = {21},
number = {4},
year = {2019},
doi = {10.23638/DMTCS-21-4-5},
language = {en},
url = {http://geodesic.mathdoc.fr/articles/10.23638/DMTCS-21-4-5/}
}
TY - JOUR AU - Goedgebeur, Jan AU - Zamfirescu, Carol T. TI - On almost hypohamiltonian graphs JO - Discrete mathematics & theoretical computer science PY - 2019 VL - 21 IS - 4 PB - mathdoc UR - http://geodesic.mathdoc.fr/articles/10.23638/DMTCS-21-4-5/ DO - 10.23638/DMTCS-21-4-5 LA - en ID - DMTCS_2019_21_4_a2 ER -
Goedgebeur, Jan; Zamfirescu, Carol T. On almost hypohamiltonian graphs. Discrete mathematics & theoretical computer science, Tome 21 (2019) no. 4. doi: 10.23638/DMTCS-21-4-5
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