From 999db74bb78ccded11230933ff5d247c51040a29 Mon Sep 17 00:00:00 2001
From: Nat Lasseter <Nat Lasseter nathan@bytemark.co.uk>
Date: Fri, 15 Dec 2017 23:14:10 +0000
Subject: Day15

---
 day15/part2 | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)
 create mode 100755 day15/part2

(limited to 'day15/part2')

diff --git a/day15/part2 b/day15/part2
new file mode 100755
index 0000000..7253a39
--- /dev/null
+++ b/day15/part2
@@ -0,0 +1,36 @@
+#!/usr/bin/env ruby
+
+class Generator
+  def initialize(iv, factor, divisor)
+    @value = iv
+    @factor = factor
+    @divisor = divisor
+  end
+
+  def next
+    n = @value
+    loop do
+      n = (n * @factor) % 2147483647
+      break if n % @divisor == 0
+    end
+    @value = n
+    return n
+  end
+end
+
+input = $stdin.readlines.map(&:chomp)
+
+ga = Generator.new(input[0].split[4].to_i, 16807, 4)
+gb = Generator.new(input[1].split[4].to_i, 48271, 8)
+
+matches = 0
+
+Mask = 2**16
+
+5_000_000.times do
+  a = ga.next % Mask
+  b = gb.next % Mask
+  matches += 1 if a == b
+end
+
+p matches
-- 
cgit v1.2.3