2016 Update

Task/Knapsack-problem-Continuous/Elixir/knapsack-problem-continuous-1.elixir

@@ -0,0 +1,36 @@
+defmodule KnapsackProblem do
+  def select( max_weight, items ) do
+    Enum.sort_by( items, fn {_name, weight, price} -> - price / weight end )
+    |> Enum.reduce( {max_weight, []}, &select_until/2 )
+    |> elem(1)
+    |> Enum.reverse
+  end
+
+  def task( items, max_weight ) do
+    IO.puts "The robber takes the following to maximize the value"
+    Enum.each( select( max_weight, items ), fn {name, weight} ->
+      :io.fwrite("~.2f of ~s~n", [weight, name])
+    end )
+  end
+
+  defp select_until( {name, weight, _price}, {remains, acc} ) when remains > 0 do
+    selected_weight = select_until_weight( weight, remains )
+    {remains - selected_weight, [{name, selected_weight} | acc]}
+  end
+  defp select_until( _item, acc ), do: acc
+
+  defp select_until_weight( weight, remains ) when weight < remains, do: weight
+  defp select_until_weight( _weight, remains ), do: remains
+end
+
+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} ]
+
+KnapsackProblem.task( items, 15 )