78 lines
2.5 KiB
Elixir
78 lines
2.5 KiB
Elixir
defmodule Day1 do
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def part1(input) do
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input
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|> Enum.map(fn line ->
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numbers = filter_digits(line)
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String.to_integer(String.first(numbers) <> String.last(numbers))
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end)
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|> Enum.sum()
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end
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def filter_digits(<<>>), do: <<>>
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def filter_digits(<<x, rest::binary>>) when x in ?1..?9, do: <<x>> <> filter_digits(rest)
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def filter_digits(<<_, rest::binary>>), do: filter_digits(rest)
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def part2(input) do
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input
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|> Enum.map(fn line ->
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numbers = filter_digits2(line)
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String.to_integer(String.first(numbers) <> String.last(numbers))
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end)
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|> Enum.sum()
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end
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def filter_digits2(<<>>), do: <<>>
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def filter_digits2(<<x, rest::binary>>) when x in ?1..?9, do: <<x>> <> filter_digits2(rest)
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def filter_digits2(<<"one", rest::binary>>), do: "1" <> filter_digits2("e" <> rest)
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def filter_digits2(<<"two", rest::binary>>), do: "2" <> filter_digits2("o" <> rest)
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def filter_digits2(<<"three", rest::binary>>), do: "3" <> filter_digits2("e" <> rest)
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def filter_digits2(<<"four", rest::binary>>), do: "4" <> filter_digits2(rest)
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def filter_digits2(<<"five", rest::binary>>), do: "5" <> filter_digits2("e" <> rest)
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def filter_digits2(<<"six", rest::binary>>), do: "6" <> filter_digits2(rest)
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def filter_digits2(<<"seven", rest::binary>>), do: "7" <> filter_digits2("n" <> rest)
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def filter_digits2(<<"eight", rest::binary>>), do: "8" <> filter_digits2("t" <> rest)
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def filter_digits2(<<"nine", rest::binary>>), do: "9" <> filter_digits2("e" <> rest)
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def filter_digits2(<<_, rest::binary>>), do: filter_digits2(rest)
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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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String.split(input, "\n", trim: true)
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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("#{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 day1.exs input_filename")
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end
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end
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Day1.run()
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