From d753c73ce1842ff664efe510ddd5556b563cfb94 Mon Sep 17 00:00:00 2001
From: Jeremy Kaplan <jdkaplan@metagram.net>
Date: Sun, 6 Dec 2020 13:13:25 -0800
Subject: [PATCH] Day 6 Part 2

---
 2020/day6/day6.ex | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/2020/day6/day6.ex b/2020/day6/day6.ex
index 9b21b55..38ee7da 100644
--- a/2020/day6/day6.ex
+++ b/2020/day6/day6.ex
@@ -16,6 +16,22 @@ defmodule Day6 do
     |> 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()