The bible of coding challenges is Cracking the Coding Interview. The book contains a good source of explanations, problems and even hints on how to solve many of them, as well as solutions.

We recommend reading the Abridged Problems version that includes some of the theory behind interviewing challenges, as well as the technical bases to solve the challenges themselves.

NeetCode is a free platform to practice mostly javascript challenges. The paid version supports other languages.

HackerRank is a freemium platform for developers. It includes Interview Prepping kits like https://www.hackerrank.com/interview/preparation-kits