From ac0e849c119cc3cd9709e57521365dd6dc5215a6 Mon Sep 17 00:00:00 2001
From: Nat Lasseter <user@4574.co.uk>
Date: Mon, 3 Dec 2018 12:14:31 +0000
Subject: Replace list with array. Obvious optimisation.

---
 day01/part2 | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/day01/part2 b/day01/part2
index d48de47..506d995 100755
--- a/day01/part2
+++ b/day01/part2
@@ -3,15 +3,21 @@
 input = $stdin.readlines.map(&:to_i)
 
 lf = 0
-freq = [0]
+posifreq = [true]
+negifreq = []
 
 loop do
 	input.each do |i|
 		lf += i
-		if freq.include?(lf)
+		if  lf >= 0 && posifreq[lf]  ||
+        lf < 0  && negifreq[-lf]
 			puts lf
 			exit
 		end
-		freq << lf
+    if lf >= 0
+  		posifreq[lf] = true
+    else
+      negifreq[-lf] = true
+    end
 	end
 end
-- 
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