47 lines
978 B
Elixir
47 lines
978 B
Elixir
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defmodule AOC.Day9 do
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@preamble_len 25
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def find_invalid(queue, [hd | tl]) do
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sums =
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:queue.to_list(queue)
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|> Combination.combine(2)
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|> Enum.map(&Enum.sum/1)
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queue =
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:queue.in(hd, queue)
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|> :queue.drop()
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if hd in sums do
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find_invalid(queue, tl)
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else
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hd
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end
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end
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def find_weakness(invalid, [_ | tl] = nums) do
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result =
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Enum.reduce_while(nums, {0, []}, fn num, {sum, l} ->
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sum = sum + num
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if sum < invalid, do: {:cont, {sum, [num | l]}}, else: {:halt, {sum, l}}
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end)
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case result do
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{sum, l} when sum == invalid -> Enum.min_max(l)
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_ -> find_weakness(invalid, tl)
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end
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end
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def parts do
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input = AOC.Util.input_integers(9, 1)
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{preamble, nums} = Enum.split(input, @preamble_len)
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invalid =
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preamble
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|> :queue.from_list()
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|> find_invalid(nums)
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{min, max} = find_weakness(invalid, input)
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{invalid, min + max}
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end
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end
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