85 lines
2.3 KiB
Elixir
85 lines
2.3 KiB
Elixir
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#!/usr/bin/env elixir
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defmodule Day6 do
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def part1({max_x, max_y, {x, y}, obstacles}) do
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walk(x, y, max_x, max_y, obstacles, MapSet.new(), 0, -1)
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|> MapSet.size()
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end
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def walk(x, y, max_x, max_y, _obstacles, visited, _x_dir, _) when x == max_x or y == max_y do
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visited
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end
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def walk(x, y, max_x, max_y, obstacles, visited, x_dir, y_dir) do
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next_x = x + x_dir
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next_y = y + y_dir
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if MapSet.member?(obstacles, {next_x, next_y}) do
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{x_dir, y_dir} = turn_right(x_dir, y_dir)
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walk(x, y, max_x, max_y, obstacles, visited, x_dir, y_dir)
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else
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visited = MapSet.put(visited, {x, y})
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walk(next_x, next_y, max_x, max_y, obstacles, visited, x_dir, y_dir)
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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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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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|> Tuple.delete_at(0)
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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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