From 8f4d06e24de19cf9c896bb9ba2cf7110e02f810b Mon Sep 17 00:00:00 2001
From: Adam Millerchip <adam@millerchip.net>
Date: Thu, 10 Dec 2020 00:30:54 +0900
Subject: [PATCH] Fix unused optimization in forms_pair?/4

---
 day9/day9part1.exs | 10 ++++------
 day9/day9part2.exs | 10 ++++------
 2 files changed, 8 insertions(+), 12 deletions(-)

diff --git a/day9/day9part1.exs b/day9/day9part1.exs
index 057d207..82b1b1a 100644
--- a/day9/day9part1.exs
+++ b/day9/day9part1.exs
@@ -20,7 +20,6 @@ defmodule Day9Part1 do
   end
 
   def sum_in_preamble?([], _max, _number), do: false
-
   def sum_in_preamble?([preamble_head | _], max, _number) when preamble_head >= max, do: false
 
   def sum_in_preamble?([preamble_head | preamble_rest], max, number) do
@@ -31,11 +30,10 @@ defmodule Day9Part1 do
     end
   end
 
-  def forms_pair?(_, [y | _], max, _number) when y > max, do: false
-
-  def forms_pair?(x, preamble_rest, _max, number) do
-    Enum.any?(preamble_rest, fn y -> x + y == number end)
-  end
+  def forms_pair?(_x, [y | _], max, _number) when y > max, do: false
+  def forms_pair?(_x, [], _max, _number), do: false
+  def forms_pair?(x, [y | _], _max, number) when x + y == number, do: true
+  def forms_pair?(x, [_y | rest], max, number), do: forms_pair?(x, rest, max, number)
 end
 
 Day9Part1.run()
diff --git a/day9/day9part2.exs b/day9/day9part2.exs
index e563478..6e0307c 100644
--- a/day9/day9part2.exs
+++ b/day9/day9part2.exs
@@ -50,7 +50,6 @@ defmodule Day9Part1 do
   end
 
   def sum_in_preamble?([], _max, _number), do: false
-
   def sum_in_preamble?([preamble_head | _], max, _number) when preamble_head >= max, do: false
 
   def sum_in_preamble?([preamble_head | preamble_rest], max, number) do
@@ -61,11 +60,10 @@ defmodule Day9Part1 do
     end
   end
 
-  def forms_pair?(_, [y | _], max, _number) when y > max, do: false
-
-  def forms_pair?(x, preamble_rest, _max, number) do
-    Enum.any?(preamble_rest, fn y -> x + y == number end)
-  end
+  def forms_pair?(_x, [y | _], max, _number) when y > max, do: false
+  def forms_pair?(_x, [], _max, _number), do: false
+  def forms_pair?(x, [y | _], _max, number) when x + y == number, do: true
+  def forms_pair?(x, [_y | rest], max, number), do: forms_pair?(x, rest, max, number)
 end
 
 Day9Part2.run()