When Trees Collide: An Approximation Algorithm for theGeneralized Steiner Problem on Networks
SIAM Journal on Computing
A General Approximation Technique for Constrained Forest Problems
SIAM Journal on Computing
On-line algorithms for Steiner tree problems (extended abstract)
STOC '97 Proceedings of the twenty-ninth annual ACM symposium on Theory of computing
Improved approximation algorithms for network design problems
SODA '94 Proceedings of the fifth annual ACM-SIAM symposium on Discrete algorithms
On-line generalized Steiner problem
Theoretical Computer Science - Special issue: Online algorithms in memoriam, Steve Seiden
Online and stochastic survivable network design
Proceedings of the forty-first annual ACM symposium on Theory of computing
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In the generalized Steiner tree problem, we find a minimumcost set of edges to connect a given set of source-sink pairs. In the online version of this problem, the source-sink pairs arrive over time. Agrawal, Klein, and Ravi give a 2-approximation algorithm for the offline problem; Berman and Coulston give an O(log n)-competitive algorithm for the online problem. Goemans and Williamson subsequently generalized the offline algorithm of Agrawal et al. to handle a large class of problems they called constrained forest problems, and other problems, such as the prize-collecting Steiner tree problem. In this paper, we show how to combine the ideas of Goemans and Williamson and those of Berman and Coulston to give an O(log n)-competitive algorithm for online constrained forest problems, including an online version of the prize-collecting Steiner tree problem.