57 lines
1.2 KiB
Elixir
57 lines
1.2 KiB
Elixir
defmodule Mix.Tasks.Day9 do
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use Mix.Task
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def run(_) do
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{_, content} = File.read("./input/2023_9.txt")
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solve(content)|> inspect() |> IO.puts()
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end
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def solve(content) do
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content
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|> String.split("\n")
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|> Stream.reject(&(&1 === ""))
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|> Stream.map(fn line ->
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line
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|> String.split(" ")
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|> Stream.map(&String.to_integer/1)
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|> Enum.to_list()
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end)
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|> Stream.map(fn list ->
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IO.puts(inspect(list))
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extrapolate(list)
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end)
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|> Enum.reduce([],
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fn l, acc ->
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[l |> Enum.sum()
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| acc]
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end) |> Enum.sum()
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end
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def extrapolate(list) do
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extrapolate(list, [])
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end
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def to_difference_list(nums) do
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IO.puts("differencing #{inspect(nums)}")
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list = nums
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|> Stream.chunk_every(2, 1, :discard)
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|> Enum.reduce([], fn [a,b], acc -> [ b - a | acc] end)
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IO.puts("differenc was #{inspect(list)}")
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list
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end
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def extrapolate([0], acc) do
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[0 | acc]
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end
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def extrapolate(list, acc) do
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IO.puts("extrapolating #{inspect(list)}")
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extrapolate(
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list |> to_difference_list() |> Enum.reverse(),
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[list |> List.last() | acc]
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)
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end
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end
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