diff --git a/2024/day14.exs b/2024/day14.exs new file mode 100755 index 0000000..ae72a9b --- /dev/null +++ b/2024/day14.exs @@ -0,0 +1,75 @@ +#!/usr/bin/env elixir +defmodule Day14 do + def part1({robots, size_x, size_y}) do + mid_x = div(size_x, 2) + mid_y = div(size_y, 2) + + robots + |> Enum.reduce({0, 0, 0, 0}, fn [px, py, vx, vy], {a, b, c, d} -> + x = Integer.mod(px + vx * 100, size_x) + y = Integer.mod(py + vy * 100, size_y) + + case {x, y} do + {x, y} when x < mid_x and y < mid_y -> {a + 1, b, c, d} + {x, y} when x < mid_x and y > mid_y -> {a, b + 1, c, d} + {x, y} when x > mid_x and y < mid_y -> {a, b, c + 1, d} + {x, y} when x > mid_x and y > mid_y -> {a, b, c, d + 1} + {x, y} when x == mid_x or y == mid_y -> {a, b, c, d} + end + end) + |> Tuple.product() + end + + def part2({robots, size_x, size_y}) do + :not_done_yet + end + + def input do + with [input_filename, size_x, size_y] <- System.argv(), + {:ok, input} <- File.read(input_filename), + {size_x, ""} <- Integer.parse(size_x), + {size_y, ""} <- Integer.parse(size_y) do + robots = + input + |> String.split(["p=", ",", " ", "v=", "\n"], trim: true) + |> Enum.map(&String.to_integer/1) + |> Enum.chunk_every(4) + + {robots, size_x, size_y} + 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("#{inspect(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 day14.exs input_filename size_x size_y") + end +end + +Day14.run()