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arXiv · 2605.09821

Online Steiner Forest with Recourse

Yaowei Long·Sepideh Mahabadi·Sherry Sarkar·Jakub Tarnawski
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Abstract

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 $\Theta(\log n)$. 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.

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Yaowei Long, Sepideh Mahabadi, Sherry Sarkar, Jakub Tarnawski. 2026-05-10. Online Steiner Forest with Recourse. https://arxiv.org/abs/2605.09821

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