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 Wroc�aw, 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.