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.