This book constitutes the refereed proceedings of the 42nd National Conference on Theoretical Computer Science, NCTCS 2024, held in Qingdao, China, during July 19-21, 2024. The 13 full papers included in this book were carefully reviewed and selected from 75 submissions. They were organized in topical sections as follows: Algorithm Design, Approximation Algorithms, Logics, and Artificial Intelligence Theory and Algorithm, Algorithm Application.