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day1 solution #2

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ab62979
day1
Sep 24, 2019
306b79e
Trigger Travis
Sep 24, 2019
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Sep 24, 2019
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Sep 24, 2019
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15 changes: 12 additions & 3 deletions lib/day1.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -25,7 +25,8 @@ defmodule AocKata.Day1 do
"""
@spec resulting_frequency(Enumerable.t()) :: integer
def resulting_frequency(frequency_changes) do
# TODO implement
frequency_changes
|> Enum.reduce(0, &(String.to_integer(&1) + &2))
end

@doc """
Expand Down Expand Up @@ -55,8 +56,16 @@ defmodule AocKata.Day1 do
"""
@spec resulting_frequency_fixed(Enumerable.t()) :: integer
def resulting_frequency_fixed(frequency_changes) do
frequency_changes = Stream.repeatedly(fn -> frequency_changes end) |> Stream.flat_map(& &1)
frequency_changes
|> Stream.cycle()
|> Enum.reduce_while({0, %{0 => true}}, fn change, {frequency, reached_frequencies} ->
frequency = frequency + String.to_integer(change)

# TODO
if reached_frequencies[frequency] do
{:halt, frequency}
else
{:cont, {frequency, Map.put(reached_frequencies, frequency, true)}}
end
end)
end
end