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'Between 1955 and 1967, the problem of “how do we de­ter­mine if there is a cycle in a linked list without mod­i­fy­ing the list” was an open problem. Meaning, any number of PhD can­di­dates in Math­e­mat­ics or Com­puter Science could have written about it as part of their dis­ser­ta­tion. With all of those hun­dreds and hun­dreds of minds, this problem re­mained open for 12 years.'

Were there any computer science graduate programs between 1955 and 1967?

You're not dealing with "hundreds and hundreds of minds", you're dealing with those minds who 1) heard about linked lists, 2) heard about or realized there was a cycle detection problem, and 3) devoted any energy to that problem as opposed to the myriad other problems available to a mathematics or electrical engineering graduate student. All of this has to have happened between 1955 and when the problem was solved in advance of starting to write the paper on it, in advance of publication of the paper in 1967. The paper also presumably included a proof of correctness that isn't being asked for in the interview.

The interviewee has the further advantage that they know there is an answer in the space of the constraints the interviewer has drawn. As they suggest less optimal solutions, those constraints get tighter, and the answer gets easier to find. If they have been through an undergraduate computer science course, they probably also have more familiarity with linked lists than most of the people attempting to solve the problem before 1967.

None of which is to say that failing to find the answer deserves disqualification - that's probably still unreasonable - but the picture is nowhere near as absurd as presented.



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