,
Tim Ophelders
,
Anna Schenfisch
,
Julia Sollberger
Creative Commons Attribution 4.0 International license
A fixed set of vertices in the plane may have multiple planar straight-line triangulations in which the degree of each vertex is the same. As such, the degree information does not completely determine the triangulation. We show that even if we know, for each vertex, the number of neighbors in each of the four cardinal directions, the triangulation is not completely determined. We show that counting such triangulations is #P-hard via a reduction from #3-regular bipartite planar vertex cover. pty
@InProceedings{chambers_et_al:LIPIcs.GD.2025.46,
author = {Chambers, Erin and Ophelders, Tim and Schenfisch, Anna and Sollberger, Julia},
title = {{Counting Triangulations of Fixed Cardinal Degrees}},
booktitle = {33rd International Symposium on Graph Drawing and Network Visualization (GD 2025)},
pages = {46:1--46:4},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-403-1},
ISSN = {1868-8969},
year = {2025},
volume = {357},
editor = {Dujmovi\'{c}, Vida and Montecchiani, Fabrizio},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.GD.2025.46},
URN = {urn:nbn:de:0030-drops-250325},
doi = {10.4230/LIPIcs.GD.2025.46},
annote = {Keywords: Planar Triangulations, Degree Information, #P-Hardness}
}