The authors sell official PDF and physical versions through Lulu and Amazon .
4.7/5 Target Audience: Competitive programmers (beginners to intermediate), ICPC / IOI aspirants, coding interview preppers. Competitive Programming 4 - Book 1 Pdf Github
While the full PDF of Book 1 is a commercial product, the authors provide extensive free support through GitHub and companion platforms: The authors sell official PDF and physical versions