69 lines
1.8 KiB
Elixir
Executable file
69 lines
1.8 KiB
Elixir
Executable file
#!/usr/bin/env elixir
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defmodule Day6 do
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def part1(input) do
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input
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|> Enum.map(fn line -> Enum.map(line, &String.to_integer/1) end)
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|> Enum.zip()
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|> Enum.map(fn {race, record} -> count_winning(race, record) end)
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|> Enum.product()
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end
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def count_winning(race, record) do
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scores = for n <- 1..div(race, 2), do: n * (race - n)
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[_middle | rev_no_middle] = reversed = Enum.reverse(scores)
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scores = scores ++ if rem(race, 2) == 1, do: reversed, else: rev_no_middle
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Enum.count(scores, fn score -> score > record end)
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end
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def part2(input) do
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[race, record] = Enum.map(input, fn line -> line |> Enum.join() |> String.to_integer() end)
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count_winning(race, record)
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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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line
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|> String.split()
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|> Enum.drop(1)
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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 day6.exs input_filename")
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end
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end
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Day6.run()
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