118 lines
3.1 KiB
Elixir
Executable file
118 lines
3.1 KiB
Elixir
Executable file
#!/usr/bin/env elixir
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defmodule Day15 do
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def part1({warehouse, robot, moves}) do
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attempt_moves(moves, robot, warehouse)
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|> Enum.map(fn
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{{x, y}, :box} -> x + y * 100
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_ -> 0
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end)
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|> Enum.sum()
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end
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def attempt_moves([], _robot, warehouse), do: warehouse
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def attempt_moves([move | next_moves], robot, warehouse) do
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next = move.(robot)
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case Map.fetch(warehouse, next) do
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:error ->
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attempt_moves(next_moves, next, warehouse)
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{:ok, :wall} ->
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attempt_moves(next_moves, robot, warehouse)
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{:ok, :box} ->
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case get_pushable_boxes(next, move, warehouse, [next]) do
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:wall ->
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attempt_moves(next_moves, robot, warehouse)
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boxes ->
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warehouse =
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Enum.reduce(boxes, warehouse, fn box, warehouse ->
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warehouse |> Map.delete(box) |> Map.put(move.(box), :box)
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end)
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attempt_moves(next_moves, next, warehouse)
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end
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end
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end
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def get_pushable_boxes(box, move, warehouse, pushable_boxes) do
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next = move.(box)
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case Map.fetch(warehouse, next) do
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:error -> pushable_boxes
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{:ok, :wall} -> :wall
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{:ok, :box} -> get_pushable_boxes(next, move, warehouse, [next | pushable_boxes])
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end
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end
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def part2(_input) do
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:boring_skipped
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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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[raw_map, raw_moves] = String.split(input, "\n\n")
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{_, _y, robot, map} =
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for <<char::binary-1 <- raw_map <> "\n">>, reduce: {0, 0, nil, %{}} do
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{x, y, robot, map} ->
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case char do
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"." -> {x + 1, y, robot, map}
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"#" -> {x + 1, y, robot, Map.put(map, {x, y}, :wall)}
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"O" -> {x + 1, y, robot, Map.put(map, {x, y}, :box)}
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"@" -> {x + 1, y, {x, y}, map}
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"\n" -> {0, y + 1, robot, map}
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end
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end
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moves =
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for <<char::binary-1 <- String.replace(raw_moves, "\n", "")>> do
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case char do
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"^" -> fn {x, y} -> {x, y - 1} end
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"v" -> fn {x, y} -> {x, y + 1} end
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"<" -> fn {x, y} -> {x - 1, y} end
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">" -> fn {x, y} -> {x + 1, y} end
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end
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end
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{map, robot, moves}
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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 day15.exs input_filename")
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end
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end
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Day15.run()
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