Solution for Day 04

day_04/second.rb

@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+input = File.read('./input').split("\n\n")
+
+required = %w[byr iyr eyr hgt hcl ecl pid]
+
+def valid?(key, value)
+  case key
+  when 'byr'
+    value.to_i.between? 1920, 2002
+  when 'iyr'
+    value.to_i.between? 2010, 2020
+  when 'eyr'
+    value.to_i.between? 2020, 2030
+  when 'hgt'
+    _, num, unit = *value.match(/(\d+)(.+)/)
+    case unit
+    when 'cm'
+      num.to_i.between? 150, 193
+    when 'in'
+      num.to_i.between? 59, 76
+    end
+  when 'hcl'
+    !!value[/\A#[0-9a-f]{6}\z/]
+  when 'ecl'
+    %w[amb blu brn gry grn hzl oth].include? value
+  when 'pid'
+    !!value[/\A[0-9]{9}\z/]
+  end
+end
+
+out = input.map do |passport|
+  values = passport.split /[\s|\n]/
+  
+  required.map do |key|
+    key, value = values.find{|v| v.start_with? key}&.split ':'
+    valid?(key, value)
+  end.inject(:&)
+end
+puts out.count(true)