92 lines
2.5 KiB
Elixir
Executable file
92 lines
2.5 KiB
Elixir
Executable file
#!/usr/bin/env elixir
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defmodule Patrol do
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defstruct obstacles: MapSet.new(),
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visited: MapSet.new(),
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x: 0,
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y: 0,
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max_x: nil,
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max_y: nil,
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dir_x: 0,
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dir_y: -1
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end
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defmodule Day6 do
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def part1(%Patrol{} = patrol) when patrol.x == patrol.max_x or patrol.y == patrol.max_y do
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MapSet.size(patrol.visited)
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end
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def part1(%Patrol{} = patrol) do
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next_x = patrol.x + patrol.dir_x
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next_y = patrol.y + patrol.dir_y
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if MapSet.member?(patrol.obstacles, {next_x, next_y}) do
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{dir_x, dir_y} = turn_right(patrol.dir_x, patrol.dir_y)
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part1(%Patrol{patrol | dir_x: dir_x, dir_y: dir_y})
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else
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visited = MapSet.put(patrol.visited, {patrol.x, patrol.y})
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part1(%Patrol{patrol | x: next_x, y: next_y, visited: visited})
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end
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end
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def turn_right(0, -1), do: {1, 0}
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def turn_right(1, 0), do: {0, 1}
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def turn_right(0, 1), do: {-1, 0}
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def turn_right(-1, 0), do: {0, -1}
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def part2(_input) do
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# hmmmmmmm probably need completely different solution
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:ok
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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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{_x, max_x, max_y, {x, y}, obstacles} =
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for <<char::binary-1 <- input>>, reduce: {0, 0, 0, nil, MapSet.new()} do
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{x, max_x, y, guard, obstacles} ->
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case char do
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"." -> {x + 1, max_x, y, guard, obstacles}
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"#" -> {x + 1, max_x, y, guard, MapSet.put(obstacles, {x, y})}
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"^" -> {x + 1, max_x, y, {x, y}, obstacles}
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"\n" -> {0, x, y + 1, guard, obstacles}
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end
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end
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%Patrol{x: x, y: y, max_x: max_x, max_y: max_y, obstacles: obstacles}
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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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