79 lines
2 KiB
Elixir
79 lines
2 KiB
Elixir
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#!/usr/bin/env elixir
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defmodule Day5 do
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def part1({updates, _greater?, sorted?}) do
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updates
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|> Enum.filter(sorted?)
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|> Enum.map(&Enum.at(&1, div(length(&1), 2)))
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|> Enum.sum()
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end
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def part2({updates, greater?, sorted?}) do
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updates
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|> Enum.reject(sorted?)
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|> Enum.map(&(Enum.sort(&1, greater?) |> Enum.at(div(length(&1), 2))))
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|> Enum.sum()
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end
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def input do
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with [input_filename] <- System.argv(),
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{:ok, input} <- File.read(input_filename) do
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[rules_raw, updates_raw] = String.split(input, "\n\n")
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less_than =
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String.split(rules_raw, ["|", "\n"])
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|> Enum.map(&String.to_integer/1)
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|> Enum.chunk_every(2)
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|> Enum.group_by(fn [a, _] -> a end, fn [_, b] -> b end)
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greater? = fn greater, lesser -> lesser in Map.get(less_than, greater, []) end
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sorted? = fn report ->
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report
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|> Enum.chunk_every(2, 1, :discard)
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|> Enum.all?(fn [greater, lesser] -> greater?.(greater, lesser) end)
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end
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updates =
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updates_raw
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|> String.split("\n", trim: true)
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|> Enum.map(fn row -> String.split(row, ",") |> Enum.map(&String.to_integer/1) end)
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{updates, greater?, sorted?}
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else
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_ -> :error
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end
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end
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#######################
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# HERE BE BOILERPLATE #
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#######################
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def run do
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case input() do
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:error -> print_usage()
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input -> run_parts_with_timer(input)
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end
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end
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defp run_parts_with_timer(input) do
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run_with_timer(1, fn -> part1(input) end)
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run_with_timer(2, fn -> part2(input) end)
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end
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defp run_with_timer(part, fun) do
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{time, result} = :timer.tc(fun)
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IO.puts("Part #{part} (completed in #{format_time(time)}):\n")
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IO.puts("#{inspect(result)}\n")
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end
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defp format_time(μsec) when μsec < 1_000, do: "#{μsec}μs"
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defp format_time(μsec) when μsec < 1_000_000, do: "#{μsec / 1000}ms"
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defp format_time(μsec), do: "#{μsec / 1_000_000}s"
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defp print_usage do
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IO.puts("Usage: elixir day5.exs input_filename")
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end
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end
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Day5.run()
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