68 lines
2 KiB
Elixir
68 lines
2 KiB
Elixir
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defmodule Day3 do
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def part1(input), do: move(input, MapSet.new([{0, 0}]), {0, 0})
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def move(<<?<, rest::binary>>, houses, {x, y}), do: deliver(rest, houses, {x - 1, y})
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def move(<<?>, rest::binary>>, houses, {x, y}), do: deliver(rest, houses, {x + 1, y})
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def move(<<?^, rest::binary>>, houses, {x, y}), do: deliver(rest, houses, {x, y - 1})
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def move(<<?v, rest::binary>>, houses, {x, y}), do: deliver(rest, houses, {x, y + 1})
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def move(<<>>, houses, _addr), do: MapSet.size(houses)
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def deliver(moves, houses, addr), do: move(moves, MapSet.put(houses, addr), addr)
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def part2(input), do: move2(input, MapSet.new([{0, 0}]), {0, 0}, {0, 0})
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def move2(<<ms, mb, rest::binary>>, houses, santa, bot) do
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santa = next(ms, santa)
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bot = next(mb, bot)
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move2(rest, MapSet.union(houses, MapSet.new([santa, bot])), santa, bot)
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end
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def move2(<<>>, houses, _santa, _bot), do: MapSet.size(houses)
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def next(?<, {x, y}), do: {x - 1, y}
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def next(?>, {x, y}), do: {x + 1, y}
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def next(?^, {x, y}), do: {x, y - 1}
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def next(?v, {x, y}), do: {x, y + 1}
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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("#{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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