WAOA 2005 Special Issue of TOCS

Abstract

This special issue of Theory of Computing Systems is devoted to selected papers from the 3rd Workshop on Approximation and Online Algorithms (WAOA 2005) that took place in Palma de Mallorca, Spain in October 2005. Of 68 papers submitted to the workshop, 26 were accepted and 6 were invited to this special issue. The papers in this special issue deal with several of the most fundamental topics in approximation and online algorithms: optimization problems in graphs and networks, packing problems, and scheduling problems. Some of the papers consider new variants of classical problems. Bar-Yehuda, Feldman and Rawitz investigate the convex recoloring problem for trees, a problem arising in the context of phylogenetic tree reconstruction. They present an improved approximation algorithm, based on the local ratio technique and dynamic programming, as well as a fixed-parameter tractable algorithm. Blaser and Ram study the classical traveling salesman problem in a game-theoretic setting. They prove that it is NP-hard to determine whether the core of a metric TSP game is empty or not and provide approximately fair cost allocation schemes. Han, Iwama and Zhang consider the square packing problem, a two-dimensional geometric variant of the knapsack problem, in an online setting where previously packed squares can be removed later on. They give tight bounds on the competitive ratio for the