Improved Approximations for the Max k-Colored Clustering Problem -- A o(n)-Competitive Deterministic Algorithm for Online Matching on a Line -- Better Algorithms for Online Bin Stretching -- Online Colored Bin Packing -- Improved Bound for Online Square-into-Square Packing -- Improved Approximation Algorithm for Fault-Tolerant Facility Placement -- The Submodular Facility Location Problem and the Submodular Joint Replenishment Problem -- Online Multi-Coloring with Advice -- Approximating Steiner Trees and Forests with Minimum Number of Steiner Points -- Energy-Efficient Algorithms for Non-pre-emptive Speed-Scaling -- Optimal Online and Offline Algorithms for Robot-Assisted Restoration of Barrier Coverage -- Linear-Time Approximation Algorithms for Unit Disk Graphs -- The Minimum Feasible Tileset Problem -- Online Ad Assignment with an Ad Exchange -- Minimum Linear Arrangement of Series-Parallel Graphs -- Online Dual Edge Coloring of Paths and Trees -- Online Packet Scheduling Under Adversarial Jamming -- Generalized Hypergraph Matching via Iterated Packing and Local Ratio -- Steiner Trees with Bounded RC-Delay -- Multiprocessor Jobs, Pre-emptive Schedules, and One-Competitive Online Algorithms -- Routing Under Uncertainty: The a priori Traveling Repairman Problem -- Primal-Dual Algorithms for Precedence Constrained Covering Problems.

This book constitutes the thoroughly refereed post-workshop proceedings of the 12th International Workshop on Approximation and Online Algorithms, WAOA 2014, held in Wrocław, Poland, in September 2014 as part of ALGO 2014. The 22 revised full papers presented were carefully reviewed and selected from 49 submissions. They cover a wide range of topics such as coloring and partitioning, competitive analysis, network design, packing and covering, paradigms for design and analysis of approximation and online algorithms, randomization techniques, real-world applications, and scheduling problems.