Solved Day 5

day05/solution.rb

@@ -0,0 +1,22 @@
+#!/bin/env ruby
+
+strings = File.readlines('./input').map(&:strip)
+
+bad_pairs = Regexp.new(/ab|cd|pq|xy/).freeze
+double_letters = Regexp.new(/([a-z])\1/).freeze
+three_vowels = Regexp.new(/[aeiou]/).freeze
+
+letter_pairs = Regexp.new(/([a-z]{2}).*\1/).freeze
+alternate = Regexp.new(/([a-z]).\1/).freeze
+
+part1 = strings.reject do |string|
+  bad_pairs.match?(string) == true or double_letters.match?(string) == false or string.scan(three_vowels).count < 3
+end
+
+puts part1.count
+
+part2 = strings.reject do |string|
+  letter_pairs.match?(string) == false or alternate.match?(string) == false
+end
+
+puts part2.count