This book constitutes the proceedings of the 4th International Conference on Algorithms and Discrete Applied Mathematics, CALDAM 2018, held in Guwahati, India, in February 2018. The 23 papers presented in this volume were carefully reviewed and selected from 68 submissions. They focus on topics related to efficient algorithms and data structures, their analysis (both theoretical and experimental). The mathematical problems arising thereof, and new applications of discrete mathematics, advances in existing applications and development of new tools for discrete mathematics.