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Comment by pootch | Hacker News Reader

In a recent job interview I was asked to code a doubly linked list as part of the coding part of the interview. Linked lists are patented, did me implementing this break the law?

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Is it ?? what is the patent number.

US7028023? (http://www.google.com/patents?id=Szh4AAAAEBAJ&printsec=a...)

That only covers linked lists that have multiple "next" pointers, so you can traverse it in more than one order. It's still stupidly obvious, but does not cover singly-linked lists.

Pootch was asked to implement a doubly linked list, ie a linked list with axillary pointers that allows an alternative transversal.

Ah, I misread. In that case it is claimed by that patent, but this almost certainly wouldn't hold up in court, because there's so much prior art for doubly-linked lists.

This situation would be laughable if it weren't backed up by the force of law.

How does answering an interview question violate/infringe any patent (valid or invalid).

http://en.wikipedia.org/wiki/Patent_infringement

states " The definition of patent infringement may vary by jurisdiction, but it typically includes using or selling the patented invention. In many countries, a use is required to be commercial (or to have a commercial purpose) to constitute patent infringement.[citation needed] "

Perhaps it could be an example of indirect (contributory) infringement if the company used his interview solution in a product (ie. he facilitated their infringement)? http://en.wikipedia.org/wiki/Contributory_patent_infringemen...

Pretty unlikely in this case, but I can think of interviews where I had the same concern. MegaCorp posed a problem they were having (eg. preventing radar self jamming), I told them one solution I knew of, but I was very careful to point out that it was patented less they turn around and use it.

So I share the parent's question: Can you be held liable for infringement due to a job interview answer?

Patents are not trade secrets. There's nothing illegal about communicating the contents of a patent.

That seems to be specific way of traversing Linked Lists (which ostensibly is different than all the other ways it has been done in textbooks, published code etc.) , not Linked Lists themselves. If you find a way of traversing a list in a way that has not been done before you can apply for a patent fort that technique. If i were to use that technique of traversing linked in a product that i sell, you could sue me. However, if came up with that particular, specific way of traversing a linked list in an interview, no patents are violated anywhere. That's just silly.

I. Software is mathematics. II. Mathematics are not patentable. >> Software is not patentable.

Pick a premise and argue against it. Or, don't bother: you and the US legal system are in an argument against reality. It's not a winnable argument, but sense can take a long time to percolate through obstinate stupidity.

i'm not arguing for or against patents on software, mathematics or otherwise. I'm just saying that answering an interview question about how a particular thing might be done is not in violation of any patent laws. Replace "method for traversing linked lists" with "a new technique for cutting wood using a new tool" if you feel so strongly about software patents.

That's what I believed too.

Here's one: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sec...

If you read the claims, doubly linked lists are a special case. However, the prior art for doubly linked lists goes back decades.

And this is a special case of a directed graph.

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