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Knapsack problem/Continuous: Difference between revisions
Added Erlang
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Take all the greaves
Take 3.5kg welt</pre>
=={{header|Erlang}}==
Note use of lists:foldr/2, since sort is ascending.
<lang Erlang>
-module( knapsack_problem_continuous ).
-export( [price_per_weight/1, select/2, task/0] ).
price_per_weight( Items ) -> [{Name, Weight, Price / Weight} || {Name, Weight, Price} <-Items].
select( Max_weight, Items ) ->
{_Remains, Selected_items} = lists:foldr( fun select_until/2, {Max_weight, []}, lists:keysort(3, Items) ),
Selected_items.
task() ->
Items = items(),
io:fwrite( "The robber takes the following to maximize the value~n" ),
[io:fwrite("~.2f of ~p~n", [Weight, Name]) || {Name, Weight} <- select( 15, price_per_weight(Items) )].
items() ->
[{"beef", 3.8, 36},
{"pork", 5.4, 43},
{"ham", 3.6, 90},
{"greaves", 2.4, 45},
{"flitch", 4.0, 30},
{"brawn", 2.5, 56},
{"welt", 3.7 , 67},
{"salami", 3.0, 95},
{"sausage", 5.9 , 98}
].
select_until( {Name, Weight, _Price}, {Remains, Acc} ) when Remains > 0 ->
Selected_weight = select_until_weight( Weight, Remains ),
{Remains - Selected_weight, [{Name, Selected_weight} | Acc]};
select_until( _Item, Acc ) -> Acc.
select_until_weight( Weight, Remains ) when Weight < Remains -> Weight;
select_until_weight( _Weight, Remains ) -> Remains.
</lang>
{{out}}
<pre>
11> knapsack_problem_continuous:task().
The robber takes the following to maximize the value
3.50 of "welt"
2.40 of "greaves"
2.50 of "brawn"
3.60 of "ham"
3.00 of "salami"
</pre>
=={{header|Forth}}==
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