From e13f5c8cf9a0c6d1540de00fd128337c5ba02bea Mon Sep 17 00:00:00 2001
From: Nat Lasseter <user@4574.co.uk>
Date: Thu, 19 Dec 2019 17:00:18 +0000
Subject: Day16, part2 untested, runs forever

---
 day16/part1 | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)
 create mode 100755 day16/part1

(limited to 'day16/part1')

diff --git a/day16/part1 b/day16/part1
new file mode 100755
index 0000000..f9bbd52
--- /dev/null
+++ b/day16/part1
@@ -0,0 +1,25 @@
+#!/usr/bin/env ruby
+
+BASE = [0, 1, 0, -1]
+
+input = $stdin.readlines[0].strip.chars.map(&:to_i)
+
+def get_base(n = 1, l = 0)
+  rbase = BASE.map { |b|
+    [b] * n
+  }.flatten
+  t = ((l + 1) / rbase.length) + 1
+  (rbase * t)[1..l]
+end
+
+l = input.length
+100.times do
+  newinput = []
+  l.times do |i|
+    newinput[i] = input.zip(get_base(i+1, l))
+                        .map{|a, b| a * b}.sum.abs % 10
+  end
+  input = newinput
+end
+
+puts input.join[0...8]
-- 
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