change directory names

22/lib/days/day7.ex

@@ -0,0 +1,82 @@
+defmodule AOC.Day7 do
+  use AOC.Day, day: 7
+
+  def parse_input(lines) do
+    Enum.map(lines, fn
+      "$ cd " <> arg ->
+        {:cd, arg}
+
+      "$ ls" ->
+        :ls
+
+      "dir " <> arg ->
+        {:dir, arg}
+
+      line ->
+        [size, file] = String.split(line)
+        {:file, String.to_integer(size), file}
+    end)
+  end
+
+  def part1(input) do
+    input
+    |> get_file_sizes()
+    |> get_directory_sizes()
+    |> Enum.map(fn {_, size} -> size end)
+    |> Enum.filter(&(&1 <= 100_000))
+    |> Enum.sum()
+  end
+
+  def part2(input) do
+    file_sizes = get_file_sizes(input)
+
+    total_size =
+      file_sizes
+      |> Enum.map(&elem(&1, 1))
+      |> Enum.sum()
+
+    size_needed = total_size - 40_000_000
+
+    file_sizes
+    |> get_directory_sizes()
+    |> Enum.map(&elem(&1, 1))
+    |> Enum.filter(fn size -> size >= size_needed end)
+    |> Enum.min()
+  end
+
+  def get_file_sizes(input) do
+    Enum.reduce(input, {[], []}, fn
+      {:cd, "/"}, {_, sizes} ->
+        {["/"], sizes}
+
+      {:cd, ".."}, {[_ | path], sizes} ->
+        {path, sizes}
+
+      {:cd, dir}, {path, sizes} ->
+        {[dir | path], sizes}
+
+      {:file, size, file}, {path, sizes} ->
+        {path, [{[file | path], size} | sizes]}
+
+      _, acc ->
+        acc
+    end)
+    |> elem(1)
+  end
+
+  def get_directory_sizes(file_sizes) do
+    file_sizes
+    |> Enum.reduce(%{}, fn {[_ | path], size}, acc ->
+      path = Enum.reverse(path)
+      update_directory_size(acc, size, path)
+    end)
+  end
+
+  def update_directory_size(sizes, file_size, file_path) do
+    Enum.reduce(file_path, {sizes, []}, fn dir, {sizes, cur_path} ->
+      cur_path = [dir | cur_path]
+      {Map.update(sizes, cur_path, file_size, &(&1 + file_size)), cur_path}
+    end)
+    |> elem(0)
+  end
+end