19 part 1

examples/19.txt

@@ -0,0 +1,17 @@
+px{a<2006:qkq,m>2090:A,rfg}
+pv{a>1716:R,A}
+lnx{m>1548:A,A}
+rfg{s<537:gd,x>2440:R,A}
+qs{s>3448:A,lnx}
+qkq{x<1416:A,crn}
+crn{x>2662:A,R}
+in{s<1351:px,qqz}
+qqz{s>2770:qs,m<1801:hdj,R}
+gd{a>3333:R,R}
+hdj{m>838:A,pv}
+
+{x=787,m=2655,a=1222,s=2876}
+{x=1679,m=44,a=2067,s=496}
+{x=2036,m=264,a=79,s=2244}
+{x=2461,m=1339,a=466,s=291}
+{x=2127,m=1623,a=2188,s=1013}

lib/days/16.rb

@@ -13,7 +13,7 @@ class Day16
     left: [-1, 0]
   }
 
-  Beam = Struct.new(:x, :y, :dir) do
+  Beam = Data.define(:x, :y, :dir) do
     def move(dir)
       mv = MOVEMENTS[dir]
       Beam.new(x + mv[0], y + mv[1], dir)

lib/days/19.rb

@@ -0,0 +1,90 @@
+class Day19
+
+  Rule = Data.define(:destination, :operation, :category, :value) do
+    def matches?(part)
+      return true if operation.nil?
+
+      part.send(category).send(operation, value)
+    end
+  end
+
+  Part = Struct.new(:x, :m, :a, :s) do
+    def value
+      x + m + a + s
+    end
+  end
+
+  def parse(input)
+    rule_regex = /(?<cat>[a-z])(?<op>[<>])(?<value>\d+):(?<dest>[a-zA-Z]+)/
+
+    flows_str, parts_str = input.split("\n\n")
+
+    flows = flows_str.split("\n").to_h do |line|
+      name, rest = line.split('{')
+
+      rules = rest[0...-1].split(',').map do |str|
+        if (match = str.match(rule_regex))
+          Rule.new(
+            match['dest'],
+            match['op'],
+            match['cat'].to_sym,
+            match['value'].to_i
+          )
+        else
+          Rule.new(str, nil, nil, nil)
+        end
+      end
+
+      [name, rules]
+    end
+
+    part_regex = /x=(?<x>\d+),m=(?<m>\d+),a=(?<a>\d+),s=(?<s>\d+)/
+
+    parts = parts_str.split("\n").map do |line|
+      if (match = line.match(part_regex))
+        Part.new(match['x'].to_i, match['m'].to_i, match['a'].to_i, match['s'].to_i)
+      else
+        raise "Unexpected part format #{line}!"
+      end
+    end
+
+    [flows, parts]
+  end
+
+  def part1(input)
+    flows, parts = parse(input)
+
+    accepted = []
+    rejected = []
+
+    parts.each do |part|
+      current = 'in'
+
+      loop do
+        if current == 'R'
+          rejected << part
+          break
+        elsif current == 'A'
+          accepted << part
+          break
+        end
+
+        workflow = flows[current]
+
+        workflow.each do |rule|
+          if rule.matches?(part)
+            current = rule.destination
+            break
+          end
+        end
+      end
+    end
+
+    accepted.sum(&:value)
+  end
+
+  def part2(input)
+    'TODO'
+  end
+
+end

test/19_test.rb

@@ -0,0 +1,18 @@
+require 'minitest/autorun'
+require 'minitest/pride'
+require_relative '../app'
+
+class TestDay19 < Minitest::Test
+  def setup
+    @data = File.read(File.join(APP_ROOT, 'examples', '19.txt')).rstrip
+    @day = Day19.new
+  end
+
+  def test_part1
+    assert_equal @day.part1(@data), 19114
+  end
+
+  def test_part2
+    assert_equal @day.part2(@data), ''
+  end
+end