2017 ruby day 15

ruby/2017/15/bin/problem

@@ -0,0 +1,38 @@
+#!/usr/bin/env ruby
+
+def generate(value, factor)
+  (value * factor) % 2147483647
+end
+
+line_1, line_2 = STDIN.read.chomp.split("\n").to_a
+generator_a_start = line_1.gsub("Generator A starts with ", "").to_i
+generator_b_start = line_2.gsub("Generator B starts with ", "").to_i
+
+a_factor = 16807
+b_factor = 48271
+
+a = generator_a_start
+b = generator_b_start
+pairs = 0
+
+40000000.times do
+  a = generate(a, a_factor)
+  b = generate(b, b_factor)
+  pairs += 1 if (a & 65535 == b & 65535)
+end
+
+puts "Part 1: #{pairs}"
+
+a = generator_a_start
+b = generator_b_start
+pairs = 0
+
+5000000.times do
+  a = generate(a, a_factor)
+  a = generate(a, a_factor) until (a % 4) == 0
+  b = generate(b, b_factor)
+  b = generate(b, b_factor) until (b % 8) == 0
+  pairs += 1 if (a & 65535 == b & 65535)
+end
+
+puts "Part 2: #{pairs}"