39 lines
1.0 KiB
Factor
39 lines
1.0 KiB
Factor
! Copyright (c) 2007 Samuel Tardieu.
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! See http://factorcode.org/license.txt for BSD license.
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USING: kernel math math.functions math.ranges sequences project-euler.common ;
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IN: project-euler.173
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! http://projecteuler.net/index.php?section=problems&id=173
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! DESCRIPTION
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! -----------
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! We shall define a square lamina to be a square outline with a square "hole"
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! so that the shape possesses vertical and horizontal symmetry. For example,
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! using exactly thirty-two square tiles we can form two different square
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! laminae: [see URL for figure]
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! With one-hundred tiles, and not necessarily using all of the tiles at one
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! time, it is possible to form forty-one different square laminae.
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! Using up to one million tiles how many different square laminae can be formed?
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! SOLUTION
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! --------
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<PRIVATE
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: laminae ( upper -- n )
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4 / dup sqrt [1,b] 0 rot [ over /i - - ] curry reduce ;
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PRIVATE>
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: euler173 ( -- answer )
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1000000 laminae ;
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! [ euler173 ] 100 ave-time
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! 0 ms ave run time - 0.35 SD (100 trials)
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SOLUTION: euler173
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