day 24, part 1

Author: robbkidd

2024/ruby/day24.rb

@@ -0,0 +1,106 @@
+require_relative 'day'
+
+class Day24 < Day # >
+
+  # @example
+  #   day.part1 #=> 4
+  # @example larger
+  #   day = Day24.new(EXAMPLE_LARGER)
+  #   day.part1 #=> 2024
+  def part1
+    known_wires = {}
+    to_be_determined = {}
+    input
+      .split("\n")
+      .each do |line|
+        case line
+        when /\: /
+          wire, signal = line.split(": ")
+          known_wires[wire] = signal.to_i
+        when /-\>/
+          input1, gate, input2, wire = line.scan(/\w+/)
+          to_be_determined[wire] = { inputs: [input1, input2], gate: gate }
+        end
+      end
+
+    while to_be_determined.keys.any? {|wire| wire.start_with?('z') } do
+      puts to_be_determined.keys.inspect if ENV['DEBUG']
+      to_be_determined
+        .select {|wire, data| data[:inputs].all? {|input| known_wires.keys.include?(input) } }
+        .each do |wire, data|
+          known_wires[wire] =
+            case data[:gate]
+            when 'AND' ; known_wires[data[:inputs][0]] & known_wires[data[:inputs][1]]
+            when 'OR'  ; known_wires[data[:inputs][0]] | known_wires[data[:inputs][1]]
+            when 'XOR' ; known_wires[data[:inputs][0]] ^ known_wires[data[:inputs][1]]
+            else ; raise "lolwut: unknown gate #{data[:gate]}"
+            end
+          to_be_determined.delete(wire)
+        end
+    end
+
+    known_wires
+      .select {|wire, signal| wire.start_with?('z') }
+      .sort_by {|wire, signal| wire }
+      .reverse
+      .map {|wire, signal| signal.to_s }
+      .join
+      .to_i(2)
+  end
+
+  # @example
+  #   day.part2 #=> 'how are you'
+  def part2
+  end
+
+  EXAMPLE_INPUT = File.read("../inputs/day24-example-input.txt")
+  EXAMPLE_LARGER = <<~LARGER
+    x00: 1
+    x01: 0
+    x02: 1
+    x03: 1
+    x04: 0
+    y00: 1
+    y01: 1
+    y02: 1
+    y03: 1
+    y04: 1
+
+    ntg XOR fgs -> mjb
+    y02 OR x01 -> tnw
+    kwq OR kpj -> z05
+    x00 OR x03 -> fst
+    tgd XOR rvg -> z01
+    vdt OR tnw -> bfw
+    bfw AND frj -> z10
+    ffh OR nrd -> bqk
+    y00 AND y03 -> djm
+    y03 OR y00 -> psh
+    bqk OR frj -> z08
+    tnw OR fst -> frj
+    gnj AND tgd -> z11
+    bfw XOR mjb -> z00
+    x03 OR x00 -> vdt
+    gnj AND wpb -> z02
+    x04 AND y00 -> kjc
+    djm OR pbm -> qhw
+    nrd AND vdt -> hwm
+    kjc AND fst -> rvg
+    y04 OR y02 -> fgs
+    y01 AND x02 -> pbm
+    ntg OR kjc -> kwq
+    psh XOR fgs -> tgd
+    qhw XOR tgd -> z09
+    pbm OR djm -> kpj
+    x03 XOR y03 -> ffh
+    x00 XOR y04 -> ntg
+    bfw OR bqk -> z06
+    nrd XOR fgs -> wpb
+    frj XOR qhw -> z04
+    bqk OR frj -> z07
+    y03 OR x01 -> nrd
+    hwm AND bqk -> z03
+    tgd XOR rvg -> z12
+    tnw OR pbm -> gnj
+  LARGER
+end