104 lines
3.2 KiB
Factor
104 lines
3.2 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 arrays fry io kernel locals make math
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math.order math.parser math.ranges sequences sorting ;
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IN: rosetta-code.knapsack
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! http://rosettacode.org/wiki/Knapsack_problem/0-1
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! A tourist wants to make a good trip at the weekend with his
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! friends. They will go to the mountains to see the wonders of
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! nature, so he needs to pack well for the trip. He has a good
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! knapsack for carrying things, but knows that he can carry a
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! maximum of only 4kg in it and it will have to last the whole
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! day. He creates a list of what he wants to bring for the trip
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! but the total weight of all items is too much. He then decides
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! to add columns to his initial list detailing their weights and a
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! numerical value representing how important the item is for the
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! trip.
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! The tourist can choose to take any combination of items from
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! the list, but only one of each item is available. He may not cut
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! or diminish the items, so he can only take whole units of any
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! item.
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! Which items does the tourist carry in his knapsack so that
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! their total weight does not exceed 400 dag [4 kg], and their
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! total value is maximised?
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TUPLE: item
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name weight value ;
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CONSTANT: items {
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T{ item f "map" 9 150 }
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T{ item f "compass" 13 35 }
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T{ item f "water" 153 200 }
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T{ item f "sandwich" 50 160 }
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T{ item f "glucose" 15 60 }
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T{ item f "tin" 68 45 }
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T{ item f "banana" 27 60 }
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T{ item f "apple" 39 40 }
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T{ item f "cheese" 23 30 }
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T{ item f "beer" 52 10 }
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T{ item f "suntan cream" 11 70 }
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T{ item f "camera" 32 30 }
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T{ item f "t-shirt" 24 15 }
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T{ item f "trousers" 48 10 }
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T{ item f "umbrella" 73 40 }
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T{ item f "waterproof trousers" 42 70 }
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T{ item f "waterproof overclothes" 43 75 }
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T{ item f "note-case" 22 80 }
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T{ item f "sunglasses" 7 20 }
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T{ item f "towel" 18 12 }
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T{ item f "socks" 4 50 }
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T{ item f "book" 30 10 }
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}
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CONSTANT: limit 400
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: make-table ( -- table )
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items length 1 + [ limit 1 + 0 <array> ] replicate ;
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:: iterate ( item-no table -- )
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item-no table nth :> prev
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item-no 1 + table nth :> curr
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item-no items nth :> item
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limit [1,b] [| weight |
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weight prev nth
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weight item weight>> - dup 0 >=
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[ prev nth item value>> + max ]
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[ drop ] if
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weight curr set-nth
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] each ;
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: fill-table ( table -- )
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[ items length iota ] dip
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'[ _ iterate ] each ;
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:: extract-packed-items ( table -- items )
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[
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limit :> weight!
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items length iota <reversed> [| item-no |
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item-no table nth :> prev
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item-no 1 + table nth :> curr
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weight [ curr nth ] [ prev nth ] bi =
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[
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item-no items nth
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[ name>> , ] [ weight>> weight swap - weight! ] bi
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] unless
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] each
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] { } make ;
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: solve-knapsack ( -- items value )
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make-table [ fill-table ]
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[ extract-packed-items ] [ last last ] tri ;
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: knapsack-main ( -- )
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solve-knapsack
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"Total value: " write number>string print
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"Items packed: " print
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natural-sort
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[ " " write print ] each ;
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MAIN: knapsack-main
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