Best algorithms book?
Mathematical analysis: Cormen et al. https://en.wikipedia.org/wiki/Introduction_to_Algorithms
Java code: Sedgewick & Wayne https://algs4.cs.princeton.edu/home/
Organization of high-level concepts: Levitin https://www.pearson.com/us/higher-education/program/Levitin-Introduction-to-the-Design-and-Analysis-of-Algorithms-3rd-Edition/PGM223052.html
Free, online, interactive: OpenDSA https://opendsa-server.cs.vt.edu/