61 lines
1.6 KiB
Elixir
61 lines
1.6 KiB
Elixir
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#!/usr/bin/env elixir
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defmodule Day3 do
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def part1(input) do
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Regex.scan(~r/mul\((\d+),(\d+)\)/, input, capture: :all_but_first)
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|> Enum.map(fn [a, b] -> String.to_integer(a) * String.to_integer(b) end)
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|> Enum.sum()
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end
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def part2(input) do
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Regex.scan(~r/mul\((\d+),(\d+)\)|(do\(\))|(don't\(\))/, input, capture: :all_but_first)
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|> Enum.reduce({0, :process}, fn
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["", "", "do()"], {sum, _} -> {sum, :process}
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["", "", "", "don't()"], {sum, _} -> {sum, :skip}
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_, {sum, :skip} -> {sum, :skip}
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[a, b], {sum, :process} -> {sum + String.to_integer(a) * String.to_integer(b), :process}
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end)
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|> elem(0)
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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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input
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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 day3.exs input_filename")
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end
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end
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Day3.run()
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