From 424cd48fea580176a1cac5543d9d7639ac30c3fa Mon Sep 17 00:00:00 2001
From: Jeremy Kaplan <jdkaplan@metagram.net>
Date: Tue, 1 Dec 2020 23:59:19 -0800
Subject: [PATCH] Day 2 Part 2

---
 2020/day2/day2.ex | 27 +++++++++++++++++++++++----
 1 file changed, 23 insertions(+), 4 deletions(-)

diff --git a/2020/day2/day2.ex b/2020/day2/day2.ex
index 6775b06..1b5e9e8 100644
--- a/2020/day2/day2.ex
+++ b/2020/day2/day2.ex
@@ -22,7 +22,7 @@ defmodule Day2 do
     end)
   end
 
-  defp valid?(policy, password) do
+  defp valid_sled?(policy, password) do
     count =
       Enum.reduce(String.codepoints(password), 0, fn char, count ->
         if char == policy.letter do
@@ -35,12 +35,31 @@ defmodule Day2 do
     policy.min <= count and count <= policy.max
   end
 
+  defp valid_toboggan?(policy, password) do
+    chars = String.codepoints(password)
+    l1 = Enum.at(chars, policy.min - 1)
+    l2 = Enum.at(chars, policy.max - 1)
+    (l1 == policy.letter or l2 == policy.letter) and l1 != l2
+  end
+
+  defp xor(a, b) do
+    (a or b) and a != b
+  end
+
   def part1 do
     parse(read_input())
-    |> Enum.filter(fn %{policy: policy, password: password} -> valid?(policy, password) end)
+    |> Enum.filter(fn %{policy: policy, password: password} -> valid_sled?(policy, password) end)
+    |> length()
+  end
+
+  def part2 do
+    parse(read_input())
+    |> Enum.filter(fn %{policy: policy, password: password} ->
+      valid_toboggan?(policy, password)
+    end)
     |> length()
-    |> IO.inspect()
   end
 end
 
-Day2.part1()
+Day2.part1() |> IO.inspect()
+Day2.part2() |> IO.inspect()