Day 6

lib/day6/day6.ex

@@ -41,21 +41,25 @@ defmodule Day6 do
     str
     |> String.replace(~r/\s/, "")
     |> String.to_charlist()
-    |> MapSet.new()
+    |> Enum.into(MapSet.new())
   end
 
   def questions_with_all_yes(str) do
-    people =
-      str
-      |> String.split("\n")
-      |> Enum.map(fn person ->
-        person
-        |> String.to_charlist()
-        |> MapSet.new()
-      end)
+    str
+    |> String.split("\n")
+    |> Enum.map(fn person ->
+      person
+      |> String.to_charlist()
+      |> MapSet.new()
+    end)
+    |> Enum.reduce(nil, fn person, acc ->
+      case acc do
+        nil ->
+          person
 
-    people
-    |> Enum.drop(1)
-    |> Enum.reduce(List.first(people), &MapSet.intersection/2)
+        _ ->
+          MapSet.intersection(acc, person)
+      end
+    end)
   end
 end