I am a fresh software engineering graduate and I am looking for something to improve my problem solving skills, while I did learn about basic algorithms and data structures, I feel like I could learn further more, I know about big O, fast sorting algorithms, dynamic programming, backtracking, binary trees (Although I do not think I know everything about them), I also know about low level memory concepts.
I am sure I forgot to mention some of the stuff I also know about, but I hope the ones I mentioned give a good insights on where I should move onto next.
Honestly I would take a look through a good standard library that provides a lot of algorithms (e.g. C++ or Rust). That has the basics, especially for data structures.
Also have a go at some hacker rank tests. Especially if you want to learn dynamic programming (abysmal name), they absolutely love that.