An updated version of the popular book on graph theory, Graphs and Digraphs, Fourth Edition maintains its predecessor's reputation for being thorough, accurate, and complete. Over the years, the book has evolved from a completely mathematical treatment to one that also considers the needs of the computer scientist and now includes many algorithmic discussions. The problems posed are designed to teach readers how to construct various proofs and in doing so, learn the meanings of definitions and concepts. The new edition features major changes to the sections on domination, colorings, distance, and Hamiltonian graphs. The authors also added more problems and removed outdated material.