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[Sync Iteration] elixir/knapsack/1 #29

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[Sync Iteration] elixir/knapsack/1 #29

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23 changes: 23 additions & 0 deletions solutions/elixir/knapsack/1/lib/knapsack.ex
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Original file line number Diff line number Diff line change
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defmodule Knapsack do
@doc """
Return the maximum value that a knapsack can carry.
"""
@spec maximum_value(items :: [%{value: integer, weight: integer}], maximum_weight :: integer) :: integer
def maximum_value(items, maximum_weight), do: knapsack(items, maximum_weight, 0)

# No items left
defp knapsack([], _, memo), do: memo

# Item too heavy
defp knapsack([item | items], remaining_capacity, memo) when item.weight > remaining_capacity do
knapsack(items, remaining_capacity, memo)
end

# Maxium between with and without the item
defp knapsack([item | items], remaining_capacity, memo) do
max(
knapsack(items, remaining_capacity - item.weight, memo + item.value),
knapsack(items, remaining_capacity, memo)
)
end
end