It caught me out once... At the time I thought it was useless with no real practical application. But I was only fooling myself. Reasoning about linked lists is a basic fundamental and easy to solve. After I failed, I went away and studied it, and implemented it in code. Many many people can reason about it and describe the pointer manipulation at a high level, but then only 10% can actually put pen to whiteboard so to speak. It is a remarkable question. After you master that (take half a day), move onto trees and then maybe graphs. Practice modeling some problems with those data structures and after you do that any development job is yours for the taking.