49 lines
1.0 KiB
Elixir
49 lines
1.0 KiB
Elixir
defmodule Day1 do
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def calculate_frequency(shifts) do
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shifts
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|> Enum.reduce(0, &+/2)
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end
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def first_repetition(shifts, index \\ 0, sum \\ 0, seen \\ [0]) do
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sum = sum + Enum.at(shifts, index)
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next_index = rem(index + 1, Enum.count(shifts))
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cond do
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Enum.member?(seen, sum) ->
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sum
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true ->
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first_repetition(shifts, next_index, sum, [sum | seen])
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end
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end
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def first_repetition_stream(shifts) do
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shifts
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|> Stream.cycle()
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|> Enum.reduce_while({0, [0]}, fn shift, {sum, seen} ->
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sum = sum + shift
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cond do
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Enum.member?(seen, sum) -> {:halt, sum}
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true -> {:cont, {sum, [sum | seen]}}
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end
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end)
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end
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def parse_input() do
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File.read!("lib/day1/input.txt")
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|> String.split("\n")
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|> Enum.map(fn s ->
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{num, _} = Integer.parse(s)
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num
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end)
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end
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def part1() do
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parse_input()
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|> calculate_frequency()
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end
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def part2() do
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parse_input()
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|> first_repetition_stream()
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end
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end |