,
Michael Wallner
Creative Commons Attribution 4.0 International license
A relaxed k-ary tree is an ordered directed acyclic graph with a unique source and sink in which every node has out-degree k. These objects arise in the compression of trees in which some repeated subtrees are factored and repeated appearances are replaced by pointers. We prove an asymptotic theta-result for the number of relaxed k-ary tree with n nodes for n → ∞. This generalizes the previously proved binary case to arbitrary finite arity, and shows that the seldom observed phenomenon of a stretched exponential term e^{c n^{1/3}} appears in all these cases. We also derive the recurrences for compacted k-ary trees in which all subtrees are unique and minimal deterministic finite automata accepting a finite language over a finite alphabet.
@InProceedings{ghoshdastidar_et_al:LIPIcs.AofA.2024.15,
author = {Ghosh Dastidar, Manosij and Wallner, Michael},
title = {{Asymptotics of Relaxed k-Ary Trees}},
booktitle = {35th International Conference on Probabilistic, Combinatorial and Asymptotic Methods for the Analysis of Algorithms (AofA 2024)},
pages = {15:1--15:13},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-329-4},
ISSN = {1868-8969},
year = {2024},
volume = {302},
editor = {Mailler, C\'{e}cile and Wild, Sebastian},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.AofA.2024.15},
URN = {urn:nbn:de:0030-drops-204506},
doi = {10.4230/LIPIcs.AofA.2024.15},
annote = {Keywords: Asymptotic enumeration, stretched exponential, Airy function, directed acyclic graph, Dyck paths, compacted trees, minimal automata}
}
archived version