day_7.livemd

Day 7

Mix.install([:kino])

Input

input = Kino.Input.textarea("Please enter your data here")

defmodule Parser do
  def read("$ cd ..", {path, dirs}) do
    {Enum.drop(path, -1), dirs}
  end

  def read("$ cd " <> dir, {path, dirs}) do
    path = path ++ [dir]
    {path, Map.put(dirs, path, [])}
  end

  def read("dir " <> dir, {path, dirs}) do
    dir = path ++ [dir]
    dirs = Map.update!(dirs, path, fn list -> [dir | list] end)
    {path, dirs}
  end

  def read(line, {path, dirs}) do
    if Regex.match?(~r/\d+ /, line) do
      [value, _] = String.split(line, " ")
      dirs = Map.update!(dirs, path, fn list -> [String.to_integer(value) | list] end)
      {path, dirs}
    else
      {path, dirs}
    end
  end

  def sum(dirs) do
    sum(dirs[["/"]], ["/"], dirs, %{})
  end

  def sum([hd | tl], path, dirs, dir_sizes) when is_integer(hd) do
    dir_sizes = Map.update(dir_sizes, path, hd, &(&1 + hd))
    sum(tl, path, dirs, dir_sizes)
  end

  def sum([hd | tl], path, dirs, dir_sizes) do
    dir_sizes = sum(dirs[hd], hd, dirs, dir_sizes)
    value = dir_sizes[hd]
    dir_sizes = Map.update(dir_sizes, path, value, &(&1 + value))
    sum(tl, path, dirs, dir_sizes)
  end

  def sum([], _path, _dirs, dir_sizes), do: dir_sizes
end

import Parser

input =
  input
  |> Kino.Input.read()
  |> String.split("\n", trim: true)
  |> Enum.reduce({[], %{}}, &read(&1, &2))
  |> then(fn {_path, dirs} -> dirs end)
  |> sum()

space_to_free = 30_000_000 - (70_000_000 - input[["/"]])

input = Enum.map(input, fn {_k, v} -> v end)

Part 1

input
|> Enum.filter(&(&1 <= 100_000))
|> Enum.sum()

Part 2

input
|> Enum.filter(&(&1 >= space_to_free))
|> Enum.min()