It really depends. It is a bit difficult to answer this question without understanding your background first. What CS lectures have you already taken? What rela

It really depends. It is a bit difficult to answer this question without understanding your background first. What CS lectures have you already taken? What related courses (e.g., math) have you done? For example, the Stack data structure that you bring into discussion is quite simple (but interesting and important), so I am not surprised it is treated speedily. Introduction to Algorithms typically has more difficult content. Depending on this, I could recommend for example that you follow the lectures on the excellent MIT OCW YouTube channel (https://www.youtube.com/c/mitocw https://www.youtube.com/c/mitocw). But you could also do one of the numerous algorithms and data structures courses on coursera/edx. It all depends on what you know so far and what your goal is.