68 lines
2.1 KiB
Factor
68 lines
2.1 KiB
Factor
! Copyright (c) 2012 Anonymous
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! See http://factorcode.org/license.txt for BSD license.
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USING: accessors combinators kernel locals math math.order
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math.vectors sequences sequences.product combinators.short-circuit ;
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IN: rosetta-code.knapsack-unbounded
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! http://rosettacode.org/wiki/Knapsack_problem/Unbounded
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! A traveller gets diverted and has to make an unscheduled stop
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! in what turns out to be Shangri La. Opting to leave, he is
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! allowed to take as much as he likes of the following items, so
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! long as it will fit in his knapsack, and he can carry it. He
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! knows that he can carry no more than 25 'weights' in total; and
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! that the capacity of his knapsack is 0.25 'cubic lengths'.
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! Looking just above the bar codes on the items he finds their
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! weights and volumes. He digs out his recent copy of a financial
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! paper and gets the value of each item.
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! He can only take whole units of any item, but there is much
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! more of any item than he could ever carry
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! How many of each item does he take to maximise the value of
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! items he is carrying away with him?
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! Note:
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! There are four solutions that maximise the value taken. Only
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! one need be given.
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CONSTANT: values { 3000 1800 2500 }
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CONSTANT: weights { 0.3 0.2 2.0 }
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CONSTANT: volumes { 0.025 0.015 0.002 }
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CONSTANT: max-weight 25.0
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CONSTANT: max-volume 0.25
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TUPLE: bounty amounts value weight volume ;
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: <bounty> ( items -- bounty )
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[ bounty new ] dip {
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[ >>amounts ]
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[ values v. >>value ]
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[ weights v. >>weight ]
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[ volumes v. >>volume ]
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} cleave ;
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: valid-bounty? ( bounty -- ? )
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{ [ weight>> max-weight <= ]
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[ volume>> max-volume <= ] } 1&& ;
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M:: bounty <=> ( a b -- <=> )
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a valid-bounty? [
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b valid-bounty? [
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a b [ value>> ] compare
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] [ +gt+ ] if
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] [ b valid-bounty? +lt+ +eq+ ? ] if ;
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: find-max-amounts ( -- amounts )
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weights volumes [
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[ max-weight swap / ]
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[ max-volume swap / ] bi* min >integer
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] 2map ;
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: best-bounty ( -- bounty )
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find-max-amounts [ 1 + iota ] map <product-sequence>
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[ <bounty> ] [ max ] map-reduce ;
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