I get the expected value 10417.7 days for the 100-prisoner problem.

The n-prisoner problem has expected value E n , where

H=:+/ @: % @: >: @: i.
E=:* (<: + H@:<:)

The time is a sum of two geometric random variables per newly selected
prisoner, summed over all (but one) prisoners.

Best wishes,

John

Pierpaolo Bernardi wrote:
> On Tue, Sep 11, 2012 at 12:06 AM, Roger Hui <[email protected]>
> wrote:
>> V. good.
>>
>> A related question for the 100 Prisoners problem, is the expected
>> number of rounds before the prisoners go free, if each prisoner has
>> the same chance of being picked in each round.
>
> Running a simulation, without much thinking, I get around 10400 days.
>
> I'm eager to learn the proper way to compute this number, though.
>
> Cheers
> P.
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