Views : 13,833,714
Genre: Education
Date of upload: Jun 30, 2022 ^^
Rating : 4.929 (7,412/407,495 LTDR)
RYD date created : 2024-05-03T10:05:11.188464Z
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Top Comments of this video!! :3
A really incredible feature of the loop strategy is comparing how well it works even against random guessing with more chances to open boxes. For example, if each prisoner were allowed to open 99 of the 100 boxes, instead of 50, to find their own number, the total probability of success by randomly guessing is only 0.99^100, or 36.6%! (Whereas the loop strategy gives a comparable chance of success while only opening 50 boxes, and succeeds 99% of the time if you can open 99 boxes) If you were allowed to open 98 of 100 boxes, the chance of winning via random guessing drops to 13.3%, and to below 5% for 97 boxes!
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I was really confused at first on how whatever number you start with is guaranteed to be in your loop, but once I started to type out a comment questioning it I totally realized how it works. In order to finish your loop you have to end up back where you start, and since none of the boxes can be empty, you're guaranteed to be in some sort of loop.
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So, I think thereâs an easier explanation for why youâre guaranteed to eventually circle back to your own box.
For a loop to close, you have to pick a slip of a box youâve already been to (otherwise youâre just continuing on down the loop).
But the fact that youâve already been to a box requires that youâve already found its slip in a previous box.
The one exception to that, is the box you started with. Which, in this case, is your own number.
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When you first gave the solution, I sketched out on a piece of paper a version of the problem with 4 prisoners, 4 boxes, 2 attempts, and I feel like I understood the entire thing almost instantly with no further explanation required. I think lowering the numbers down to something more manageable makes the problem much more comprehensible. I mean, you could even write out 4! configurations if you wanted and prove that it works for all of them, whereas 100! is so large as to be impossible to visualize.
I think it would have been helpful to include this simpler example in the video.
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@pyguy9915
1 year ago
Something seems wrong at 9:00 What is the probability of a loop of length 1? (Can't be 1/1) Length 2?
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