Target audience is folks who never learned this stuff, or learned it but forgot it. Interesting to hear you had a different assumption from the title.
If you want something trickier, check these ones out:
https://www.interviewcake.com/question/stock-price
https://www.interviewcake.com/question/swift/find-duplicate-...
You could argue that the others are technically data structures, but I'm willing to bet most people will assume your standard list, map, heap, trie, tree, graph, etc. It's kind of like saying "Calculus for AP tests" and then only covering algebra up to Riemann sums.
Thanks for the links, I'll give them both a shot.
edit: just remembered that Calculus isn't on the SAT :)
Definitely agree that the first half of the article isn't exactly data structures yet.
But I just struggle with calling something "An inroduction to X." Have you ever heard "an introduction" and thought "oh, that's what I need!" I picture a super-dry textbook. Or one of those YouTube videos that promises to teach you how to do a thing but starts off with the person saying, "Now, before we get started..." and talks about nothing for 5 minutes before actually teaching you the thing.
Suggestion: Don't show hints for steps I already skipped. I stopped at "We can do this without destroying the input.", but had to scroll through all the hints before reaching the one I needed.
But then why would they be interviewing for a coding job anyways? Shouldn't a coder know what's a RAM, and that it's different from secondary storage??