5 ms·

484 is a perfect square. (22×22) Edit: I see you've updated your comment geocar.

• geocar 7y ago
  484 wasn't returned by the code susam originally posted. Isn’t it funny how a python one liner required two edits to produce the correct result? (The summary description still matches the old incorrect code)
  • deliciousreader 7y ago
    > The summary description still matches the old incorrect code The summary description matches the current correct code. So it could not possibly match any incorrect code (if it really existed).
    • geocar 7y ago
      > The summary description matches the current correct code. So it could not possibly match any incorrect code. Incorrect. Here's the summary reproduced (in case susam edits again): >>> There are 500 doors numbered 1, 2, ..., 500. All doors are closed initially. In iteration k, we toggle the states of doors k, 2k, ..., floor(500/k) * k where k runs from 1 to 500 Note the "floor(500/k)" statement. That matched the original code fragment (and what is still sitting in a terminal on my laptop): >>> [k**2 for k in range(1, int(500**0.5))] but not the new one which includes a +1. int(…) is floor. int(…)+1 isn't, and it's wrong: It works for 500, but not for other values. math.ceil would have been more correct, but it might've been more obvious that it doesn't match the "summary". > (if it really existed). Let me make sure I understand what you mean here: You actually think it more likely that my two implementations, written in a comment [1] with a lower timestamp than [2], and the perl6 implementation on the linked article all include 484 as part of the valid result, and yet my comment [2] that calls on this value specifically, was somehow meant to indicate that 484 is not part of the valid result? Ha. [1]: https://news.ycombinator.com/item?id=22288534 https://news.ycombinator.com/item?id=22288534 [2]: https://news.ycombinator.com/item?id=22288554 https://news.ycombinator.com/item?id=22288554
      • akovaski 7y ago
        The +1 makes the range inclusive rather than exclusive. This matches the summary, which is inclusive of floor(500/k). Ceil wouldn't correctly handle the case where the number of rooms equals a perfect square. That is, [k**2 for k in range(1, ceil(484**0.5))] does not return 484.
        • geocar 7y ago
          Quite right! So a 1+ is needed. I can't amend my comment to that point, but the original comment didn't have +1 in there anyway.