Competitive Programming 4: The Lower Bound of Programming Contests in the 2020s (Book 1: Chapters 1–4) is a comprehensive algorithmic handbook authored by Steven Halim, Felix Halim, and Suhendry Effendy. Specifically designed as an essential training guide for International Olympiad in Informatics (IOI) contestants, ICPC participants, and software engineering candidates, this volume covers fo…