Created
December 27, 2019 14:28
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Advent of Code 2019, Day3 Part 2
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| defmodule Day3Part2 do | |
| @central_port {0, 0} | |
| def run() do | |
| p1 = read_path() | |
| p2 = read_path() | |
| intersection(p1, p2) | |
| |> Enum.reject(¢ral_port?/1) | |
| |> Enum.map(fn pos -> | |
| number_of_steps(p1, pos) + number_of_steps(p2, pos) | |
| end) | |
| |> Enum.min() | |
| |> IO.puts() | |
| end | |
| def read_path() do | |
| IO.read(:line) | |
| |> String.trim() | |
| |> path_of_line() | |
| end | |
| def path_of_line(line) do | |
| line | |
| |> String.split(",") | |
| |> Enum.reduce([@central_port], fn <<direction::utf8, distance::binary>>, path -> | |
| move(path, direction, String.to_integer(distance)) | |
| end) | |
| |> Enum.reverse() | |
| end | |
| defp move(path, _, 0), do: path | |
| defp move([{x, y} | _] = path, ?R, distance), do: move([{x + 1, y} | path], ?R, distance - 1) | |
| defp move([{x, y} | _] = path, ?L, distance), do: move([{x - 1, y} | path], ?L, distance - 1) | |
| defp move([{x, y} | _] = path, ?U, distance), do: move([{x, y + 1} | path], ?U, distance - 1) | |
| defp move([{x, y} | _] = path, ?D, distance), do: move([{x, y - 1} | path], ?D, distance - 1) | |
| def intersection(p1, p2) do | |
| MapSet.intersection(MapSet.new(p1), MapSet.new(p2)) | |
| |> MapSet.to_list() | |
| end | |
| defp central_port?(coord), do: @central_port == coord | |
| def number_of_steps(path, target, steps \\ 0) | |
| def number_of_steps([{x, y} | _], {x, y}, steps), do: steps | |
| def number_of_steps([_h | t], target, steps), do: number_of_steps(t, target, steps + 1) | |
| end | |
| Day3Part2.run() |
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