https://javaspecialists.teachable.com/courses/249332/lectures/3886637
Binary tree: https://www.geeksforgeeks.org/top-50-tree-coding-problems-for-interviews/ https://www.youtube.com/watch?v=fAAZixBzIAI
Linked list: https://www.youtube.com/watch?v=Hj_rA0dhr2I
Recursion: https://www.youtube.com/watch?v=IJDJ0kBx2LM
Dynamic programming: https://www.youtube.com/watch?v=oBt53YbR9Kk