79 lines
1.9 KiB
Elixir
Executable File
79 lines
1.9 KiB
Elixir
Executable File
#!/usr/bin/env elixir
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defmodule Day4 do
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def part1(input) do
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input
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|> Enum.map(fn 0 -> 0; num_winners -> 2 ** (num_winners - 1) end)
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|> Enum.sum()
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end
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def part2(input) do
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input
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|> Enum.map(fn num_winners -> {_num_copies = 1, num_winners} end)
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|> copy()
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|> Enum.sum()
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end
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def copy([]), do: []
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def copy([{num_copies, num_winners} | rest]) do
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{to_copy, left_alone} = Enum.split(rest, num_winners)
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copied =
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Enum.map(to_copy, fn {child_num_copies, num_winners} ->
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{num_copies + child_num_copies, num_winners}
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end)
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[num_copies | copy(copied ++ left_alone)]
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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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|> String.split("\n", trim: true)
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|> Enum.map(fn line ->
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[_card_id, winning, have] = String.split(line, [": ", " | "])
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winning = winning |> String.split(" ", trim: true) |> MapSet.new()
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have = have |> String.split(" ", trim: true) |> MapSet.new()
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MapSet.intersection(winning, have) |> MapSet.size()
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end)
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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 day4.exs input_filename")
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end
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end
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Day4.run()
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