Learning resources for problem solving

Hello,

I know there is a post about learning resources for Python but I do not want learning resources for Python, I want opinions and recommendations about learning resources (not necessarily free) for problem solving, algorithms, complexity, etc...

I can start recommending a book called "Problem Solving with Algorithms and Data Structures Using Python", by Bradley N. Miller, David L. Ranum. It is available for free here: https://interactivepython.org/runestone/static/pythonds/index.html