Linked list - US Patent 7028023.Fortunately, AFAICT they are generally not in the programming world -- otherwise, being a progamming student would mean you'd be learning a bunch of patented algorithms not in an applied sense, but in the sense that you would need to know what they are so you could avoid using them* and getting sued (or learn who and how much you have to pay for the privilege).
There literally exists a patent on everything you do when you write software, unfortunately. I shouldn't have a job. People regularly patent troll - companies too (although some companies are 'defensive', applying for patents so nobody can be patent trolled for it; see Google & MapReduce.) Luckily most of these patents are completely unenforceable for the most part; it's people trying to rip off Fortune 500 companies and whatnot.
Unfortunately it seems as if nobody in the USPO actually understands software. Patents are regularly awarded to companies/individuals, and the pantents apply to totally general ideas, such as the linked list. Patents do not really make sense with software. I will let Carmack himself explain:
"The idea that I can be presented with a problem, set out to logically solve it with the tools at hand, and wind up with a program that could not be legally used because someone else followed the same logical steps some years ago and filed for a patent on it is horrifying."
It's actually reasonably well known that Dijkstra eschewed the use of computers entirely, even when he was a professor at UT Austin - he was finally pushed to buy a Mac, which he would only ever use to check email and browse the WWW until his death. A very prolific man - not only did he not believe in the need for e.g. word processors, as you could just write letters with your own hands, he believed you shouldn't need them at all, because there was no need at all for rough drafts or significant edits when one wrote. It should be in your head before you put the pen to the paper - and this is what he did.Off topic:
It is also interesting to see lots of different algorithms were developed when computers were at their infant stage or might be even before their existence.(Djikstra's algorithm for example was discovered in 1959 by him according to wikipedia)