Zero-prefix numbers

2020/day06/day6.ex

@@ -0,0 +1,37 @@
+defmodule Day6 do
+  defp read_input do
+    Path.expand('input', Path.dirname(__ENV__.file))
+    |> File.read!()
+  end
+
+  def part1 do
+    read_input()
+    |> String.split("\n\n")
+    |> Enum.map(fn block ->
+      String.split(block)
+      |> Enum.reduce(MapSet.new(), fn line, set ->
+        MapSet.union(set, MapSet.new(String.codepoints(line)))
+      end)
+    end)
+    |> Enum.map(&MapSet.size/1)
+    |> Enum.sum()
+  end
+
+  def part2 do
+    alphabet = String.codepoints("abcdefghijklmnopqrstuvwxyz")
+
+    read_input()
+    |> String.split("\n\n")
+    |> Enum.map(fn block ->
+      String.split(block)
+      |> Enum.reduce(MapSet.new(alphabet), fn line, set ->
+        MapSet.intersection(set, MapSet.new(String.codepoints(line)))
+      end)
+    end)
+    |> Enum.map(&MapSet.size/1)
+    |> Enum.sum()
+  end
+end
+
+Day6.part1() |> IO.inspect()
+Day6.part2() |> IO.inspect()