87 lines
2.2 KiB
Elixir
87 lines
2.2 KiB
Elixir
defmodule Day5 do
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def part1(input) do
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Enum.count(input, &nice?/1)
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end
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def nice?(str) do
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at_least_three_vowels(str) and
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twice_in_a_row(str) and
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not String.contains?(str, ["ab", "cd", "pq", "xy"])
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end
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def at_least_three_vowels(str) do
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str
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|> String.graphemes()
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|> Enum.frequencies()
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|> Map.take(["a", "e", "i", "o", "u"])
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|> Map.values()
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|> Enum.sum()
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|> Kernel.>=(3)
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end
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def twice_in_a_row(<<x, x, _::binary>>), do: true
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def twice_in_a_row(<<_x, rest::binary>>), do: twice_in_a_row(rest)
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def twice_in_a_row(<<>>), do: false
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def part2(input) do
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Enum.count(input, &nice2?/1)
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end
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def nice2?(str) do
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pairs = pairs(str)
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uniq = MapSet.new(pairs)
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length(pairs) > MapSet.size(uniq) and sandwich(str)
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end
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def pairs(str, prev \\ nil)
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def pairs(<<x, x, rest::binary>>, <<x, x>>), do: pairs(<<x, rest::binary>>)
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def pairs(<<x, y, rest::binary>>, _prev), do: [<<x, y>> | pairs(<<y, rest::binary>>, <<x, y>>)]
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def pairs(<<_>>, _prev), do: []
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def sandwich(<<x, y, x, _rest::binary>>), do: true
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def sandwich(<<_x, y, z, rest::binary>>), do: sandwich(<<y, z, rest::binary>>)
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def sandwich(_), do: false
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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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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 day5.exs input_filename")
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end
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end
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Day5.run()
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