On Tue, Sep 11, 2012 at 7:56 PM, Roger Hui <[email protected]> wrote:
> I am curious about how you did your simulation. What language? How much
> code?
I just transliterated Jordan's solution into code. The language is
Racket (a descendant of Scheme). The amount of code is gigantic
compared to J, but it is all straightforward, took only a few minutes.
to write.
Thanks to all for the interesting thread.
Cheers
P.
=====
(define (test number-of-prisoners rounds)
(let loop ((round rounds) (days-sum 0.0) (days-min +inf.0) (days-max -inf.0))
(if (zero? round)
(values (/ days-sum rounds) days-min days-max)
(let ((days (prisoners number-of-prisoners)))
(loop (sub1 round)
(+ days-sum days)
(min days days-min)
(max days days-max))))))
(define (prisoners number-of-prisoners)
(let loop ((days 0) (count (sub1 number-of-prisoners)) (switch 'off)
(alreay-counted (hash)))
(if (zero? count)
days
(let ((who (random number-of-prisoners)))
(if (zero? who)
(if (eq? switch 'on)
(loop (add1 days) (sub1 count) 'off alreay-counted)
(loop (add1 days) count 'off alreay-counted))
(if (eq? switch 'on)
(loop (add1 days) count 'on alreay-counted)
(if (hash-has-key? alreay-counted who)
(loop (add1 days) count 'off alreay-counted)
(loop (add1 days) count 'on (hash-set alreay-counted who
#t)))))))))
;;; EOF
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