36 lines
1.1 KiB
Factor
36 lines
1.1 KiB
Factor
! Copyright (c) 2008 Eric Mertens.
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! See http://factorcode.org/license.txt for BSD license.
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USING: kernel math math.functions sequences project-euler.common ;
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IN: project-euler.100
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! http://projecteuler.net/index.php?section=problems&id=100
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! DESCRIPTION ! -----------
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! If a box contains twenty-one coloured discs, composed of fifteen blue discs
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! and six red discs, and two discs were taken at random, it can be seen that
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! the probability of taking two blue discs, P(BB) = (15/21)*(14/20) = 1/2.
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! The next such arrangement, for which there is exactly 50% chance of taking
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! two blue discs at random, is a box containing eighty-five blue discs and
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! thirty-five red discs.
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! By finding the first arrangement to contain over 10^12 = 1,000,000,000,000
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! discs in total, determine the number of blue discs that the box would contain.
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! SOLUTION
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! --------
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: euler100 ( -- answer )
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1 1
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[ dup dup 1 - * 2 * 10 24 ^ <= ]
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[ [ 6 * swap - 2 - ] keep swap ] while nip ;
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! TODO: solution needs generalization
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! [ euler100 ] 100 ave-time
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! 0 ms ave run time - 0.14 SD (100 trials)
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SOLUTION: euler100
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