AdventOfCode/2022/day10.exs

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3.1 KiB
Elixir
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2022-12-10 15:37:38 +00:00
defmodule Day10 do
defmodule Instr do
defstruct cmd: nil, cycles: 0, amt: nil
end
def part1(input) do
process(input, _cycle = 1, _x = 1, _sample_at = 20, _sig = 0)
end
defp process([], _cycle, _x, _sample_at, sig), do: sig
defp process(instrs, cycle, x, sample_at, sig) when cycle == sample_at do
process(instrs, cycle, x, sample_at + 40, sig + cycle * x)
end
defp process([%Instr{cycles: 0} | rest], cycle, x, sample_at, sig) do
process(rest, cycle + 1, x, sample_at, sig)
end
defp process([instr = %Instr{cycles: 1, cmd: :noop} | rest], cycle, x, sample_at, sig) do
process([%Instr{instr | cycles: 0} | rest], cycle, x, sample_at, sig)
end
defp process([instr = %Instr{cycles: 1, cmd: :addx, amt: amt} | rest], cycle, x, sample_at, sig) do
process([%Instr{instr | cycles: 0} | rest], cycle, x + amt, sample_at, sig)
end
defp process([instr = %Instr{cycles: cycles} | rest], cycle, x, sample_at, sig) do
process([%Instr{instr | cycles: cycles - 1} | rest], cycle + 1, x, sample_at, sig)
end
def part2(input) do
input
|> scan(_x = 1, _pixel = 0, _pixels = [[]])
|> Enum.map(&Enum.reverse/1)
|> Enum.reverse()
|> Enum.join("\n")
end
defp scan([], _x, _pixel, pixels), do: pixels
defp scan(instrs, x, _pixel = 40, pixels) do
scan(instrs, x, _pixel = 0, [[] | pixels])
end
defp scan([%Instr{cmd: :noop} | rest], x, pixel, [row | pixels]) do
scan(rest, x, pixel + 1, [draw_pixel(pixel, x, row) | pixels])
end
defp scan([%Instr{cycles: 1, cmd: :addx, amt: amt} | rest], x, pixel, [row | pixels]) do
scan(rest, x + amt, pixel + 1, [draw_pixel(pixel, x, row) | pixels])
end
defp scan([instr = %Instr{cycles: cycles} | rest], x, pixel, [row | pixels]) do
scan([%Instr{instr | cycles: cycles - 1} | rest], x, pixel + 1, [
draw_pixel(pixel, x, row) | pixels
])
end
defp draw_pixel(pixel, x, row) when pixel in (x - 1)..(x + 1), do: ["#" | row]
defp draw_pixel(_pixel, _x, row), do: [" " | row]
def input do
with [input_filename] <- System.argv(),
{:ok, input} <- File.read(input_filename) do
input
|> String.trim()
|> String.split("\n")
|> Enum.map(fn
"noop" -> %Instr{cmd: :noop, cycles: 1}
"addx " <> x -> %Instr{cmd: :addx, cycles: 2, amt: String.to_integer(x)}
end)
else
_ -> :error
end
end
#######################
# HERE BE BOILERPLATE #
#######################
def run do
case input() do
:error -> print_usage()
input -> run_parts_with_timer(input)
end
end
defp run_parts_with_timer(input) do
run_with_timer(1, fn -> part1(input) end)
run_with_timer(2, fn -> part2(input) end)
end
defp run_with_timer(part, fun) do
{time, result} = :timer.tc(fun)
IO.puts("Part #{part} (completed in #{format_time(time)}):\n")
IO.puts("#{result}\n")
end
defp format_time(μsec) when μsec < 1_000, do: "#{μsec}μs"
defp format_time(μsec) when μsec < 1_000_000, do: "#{μsec / 1000}ms"
defp format_time(μsec), do: "#{μsec / 1_000_000}s"
defp print_usage do
IO.puts("Usage: elixir day10.exs input_filename")
end
end
Day10.run()