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.
One of the biggest things I have built was a experimental 3D physics engine, it did require some memory allocation optimizations, I built a lot of stuff I cannot really list them all in here, An honorable mention would be an FPS game from scratch without a game engine.