Invited talks -- Majority Spanning Trees, Cotrees and Their Applications -- New Transportation Problem on a Graph with Sending and Bringing-Back Operations -- Long papers -- Algorithms for Diameters of Unicycle Graphs and Diameter-Optimally Augmenting Trees -- On Short Fastest Paths in Temporal Graphs -- Minmax Regret 1-Sink Location Problems on Dynamic Flow Path Networks with Parametric Weights -- The Bike Sharing Problem -- Efficient Generation of a Card-based Uniformly Distributed Random Derangement -- Compact Data Structures for Dedekind Groups and Finite Rings -- Competitive Location Problems: Balanced Facility Location and the One-Round Manhattan Voronoi Game -- Faster Multi-Sided Boundary Labelling -- On the Geometric Red-Blue Set Cover Problem -- Fixed-Treewidth-Efficient Algorithms for Edge-Deletion to Interval Graph Classes -- $r$-Gathering Problems on Spiders: Hardness, FPT Algorithms, and PTASes -- An Improvement of Reed's Treewidth Approximation -- Homomorphisms to digraphs with large girth and oriented colorings of minimal series-parallel digraphs -- Overall and delay complexity of the CLIQUESand Bron-Kerbosch algorithms -- Computing $L(p,1)$-Labeling with Combined Parameters -- On Compatible Matchings -- Upward Point Set Embeddings of Paths and Trees -- 2-colored Point-set Embeddings of Partial 2-trees -- Better approximation algorithms for maximum weight internal spanning trees in cubic graphs and claw-free graphs -- APX-Hardness and Approximation for the $k$-Burning Number Problem -- Efficient Enumeration of Non-isomorphic Distance-Hereditary Graphs and Ptolemaic Graphs -- Physical Zero-Knowledge Proof for Ripple Effect -- Cyclic Shift Problems on Graphs -- Mathematical Characterizations and Computational Complexity of Anti-Slide Puzzles.

This book constitutes the proceedings of the 15th International Conference on Algorithms and Computation, WALCOM 2021, which was planned to take place in Yangon, Myanmar in February/March 2021. The conference changed to an online format due to the COVID-19 pandemic. The 24 full papers included in this volume were carefully reviewed and selected from a total of 60 submissions. They cover diverse areas of algorithms and computation, such as approximation algorithms, algorithmic graph theory and combinatorics, combinatorial algorithms, combinatorial optimization, computational biology, computational complexity, computational geometry, discrete geometry, data structures, experimental algorithm methodologies, graph algorithms, graph drawing, parallel and distributed algorithms, parameterized algorithms, parameterized complexity, network optimization, online algorithms, randomized algorithms, and string algorithms. .