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@adamrobbie
Created October 8, 2021 15:30
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Interview question solution
defmodule Test do
@moduledoc """
Documentation for `Test`.
"""
@spec find_stack_pair(any) :: Integer
def find_stack_pair(list) do
list
|> pairwise()
|> IO.inspect(label: "after pairing")
|> calculate()
|> List.last()
end
defp pairwise(list) do
list
|> Enum.chunk_every(2, 1, :discard)
end
defp calculate(list) do
list
|> Enum.map(&Enum.sum/1)
|> Enum.sort()
|> duplicates()
end
defp duplicates(list) do
acc_dupes = fn(x, {elems, dupes}) ->
case Map.has_key?(elems, x) do
true -> {elems, Map.put(dupes, x, nil)}
false -> {Map.put(elems, x, nil), dupes}
end
end
acc_dupes
list |> Enum.reduce({%{}, %{}}, acc_dupes) |> elem(1) |> Map.keys()
end
end
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