,
Sepideh Mahabadi
,
Sherry Sarkar
,
Jakub Tarnawski
Creative Commons Attribution 4.0 International license
In the online Steiner forest problem we are given a graph G, and a sequence of terminal pairs (u_i,v_i) which arrive in an online fashion. We are asked to maintain a low-cost subgraph in which each u_i is connected to v_i for all the pairs that have arrived so far. If we are not allowed to delete edges from our solution, then the best possible competitive ratio is Θ(log n). In this work, we initiate the study of low-recourse algorithms for online Steiner forest. We give an algorithm that maintains a constant-competitive solution and has an amortized recourse of O(log n), i.e., inserts and deletes O(log n) edges per demand on average.
@InProceedings{long_et_al:LIPIcs.ICALP.2026.141,
author = {Long, Yaowei and Mahabadi, Sepideh and Sarkar, Sherry and Tarnawski, Jakub},
title = {{Online Steiner Forest with Recourse}},
booktitle = {53rd International Colloquium on Automata, Languages, and Programming (ICALP 2026)},
pages = {141:1--141:25},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-428-4},
ISSN = {1868-8969},
year = {2026},
volume = {374},
editor = {Bhattacharya, Sayan and Nanongkai, Danupon and Benedikt, Michael and Puppis, Gabriele},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2026.141},
URN = {urn:nbn:de:0030-drops-265303},
doi = {10.4230/LIPIcs.ICALP.2026.141},
annote = {Keywords: Online algorithms with recourse, Steiner forest, Network design}
}