Cleanup of Project Euler problem 92
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! Copyright (c) 2008 Aaron Schaefer, Slava Pestov.
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! See http://factorcode.org/license.txt for BSD license.
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USING: kernel math math.ranges sequences ;
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USING: kernel math math.ranges project-euler.common sequences ;
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IN: project-euler.092
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! http://projecteuler.net/index.php?section=problems&id=92
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@ -29,7 +29,7 @@ IN: project-euler.092
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<PRIVATE
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: next-link ( n -- m )
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0 swap [ dup zero? not ] [ 10 /mod sq -rot [ + ] dip ] [ ] while drop ;
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number>digits [ sq ] sigma ;
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: chain-ending ( n -- m )
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dup [ 1 = ] [ 89 = ] bi or [ next-link chain-ending ] unless ;
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@ -40,15 +40,14 @@ IN: project-euler.092
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: fast-chain-ending ( seq n -- m )
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dup 567 > [ next-link ] when 1- swap nth ;
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: count ( seq quot -- n )
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0 -rot [ rot >r call [ r> 1+ ] [ r> ] if ] curry each ; inline
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PRIVATE>
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: euler092 ( -- answer )
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lower-endings 9999999 [1,b] [ fast-chain-ending 89 = ] with count ;
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! [ euler092 ] 10 ave-time
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! 11169 ms run / 0 ms GC ave time - 10 trials
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! 33257 ms ave run time - 624.27 SD (10 trials)
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! TODO: this solution is not very efficient, much better optimizations exist
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MAIN: euler092
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