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Solution by Max #4

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23 changes: 21 additions & 2 deletions lib/day1.ex
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Original file line number Diff line number Diff line change
Expand Up @@ -25,7 +25,7 @@ defmodule AocKata.Day1 do
"""
@spec resulting_frequency(Enumerable.t()) :: integer
def resulting_frequency(frequency_changes) do
# TODO implement
Enum.reduce(frequency_changes, 0, fn frequency, acc -> acc + get_integer(frequency) end)
end

@doc """
Expand Down Expand Up @@ -57,6 +57,25 @@ defmodule AocKata.Day1 do
def resulting_frequency_fixed(frequency_changes) do
frequency_changes = Stream.repeatedly(fn -> frequency_changes end) |> Stream.flat_map(& &1)

# TODO
{result, _} =
Enum.reduce_while(frequency_changes, {0, MapSet.new()}, fn frequency_change,
{frequency, visited_frequencies} ->
resulting_map = MapSet.put(visited_frequencies, frequency)

if MapSet.member?(visited_frequencies, frequency) do
{:halt, {frequency, resulting_map}}
else
result = frequency + get_integer(frequency_change)
{:cont, {result, resulting_map}}
end
end)

result
end

# Helper functions
defp get_integer(stringified_number) do
{number, _} = Integer.parse(stringified_number)
number
end
end