advent-of-code-2024/24/main.rb

#!/usr/bin/env ruby

input = (ARGV.first.nil? ? DATA : ARGF)
  .readlines(chomp: true)
split = input.index("")

gates = input[split+1..]
wires = input.join(" ").scan(/([a-z0-9]{3})/).flatten.uniq.map { [_1, nil] }.to_h
input[...split]
  .map { _1.split(": ") }
  .each { wires[_1] = _2.to_i }

flipped = Set.new
gates.select { _1.match?(/XOR/) }.each do |gate|
  in1, op, in2, out = gate.scan(/([a-z0-9]{3}) ([A-Z]+) ([a-z0-9]{3}) -> ([a-z0-9]{3})/).first

  if op == "XOR" && [in1, in2].map { _1[0] }.sort != %w[x y]
    if !out.start_with?("z")
      flipped << out
    end
  end
end

# 45 is a half adder
(0..44).each do |num|
  z = "z#{'%02d' % num}"
  gate = gates.find { _1.match?(/#{z}$/) }
  in1, op, in2, out = gate.scan(/([a-z0-9]{3}) ([A-Z]+) ([a-z0-9]{3}) -> ([a-z0-9]{3})/).first
  if op != "XOR"
    flipped << z
  end
end

gates.select { _1.match?(/AND/) }.each do |gate|
  in1, op, in2, out = gate.scan(/([a-z0-9]{3}) ([A-Z]+) ([a-z0-9]{3}) -> ([a-z0-9]{3})/).first

  if [in1, in2].map { _1[0] }.sort == %w[x y] && in1 != "x00"
    if gates.find { _1.match?(/#{out}/) && _1.match?(/ OR /) }.nil?
      flipped << out
    end
  end
end

gates.select { _1.match?(/XOR/) }.each do |gate|
  in1, op, in2, out = gate.scan(/([a-z0-9]{3}) ([A-Z]+) ([a-z0-9]{3}) -> ([a-z0-9]{3})/).first

  if [in1, in2].map { _1[0] }.sort == %w[x y] && in1 != "x00" && in1 != "y00"
    if gates.count { _1.match?(/#{out}/) && _1.match?(/ XOR /) } != 2
      flipped << out
    end
  end
end

i = 0
until gates.empty?
  if i >= gates.size
    i = 0
  end
  gate = gates[i]
  in1, op, in2, out = gate.scan(/([a-z0-9]{3}) ([A-Z]+) ([a-z0-9]{3}) -> ([a-z0-9]{3})/).first

  if wires[in1].nil? || wires[in2].nil?
    i += 1
    next
  end

  case op
  when "AND"
    wires[out] = wires[in1] & wires[in2]
  when "OR"
    wires[out] = wires[in1] | wires[in2]
  when "XOR"
    wires[out] = wires[in1] ^ wires[in2]
  end

  gates.delete(gate)
end

x = wires.select { _1.match?(/^x/) }.sort_by(&:first).map { _1.last.to_s }.reverse.join
xi = x.to_i(2)
y = wires.select { _1.match?(/^y/) }.sort_by(&:first).map { _1.last.to_s }.reverse.join
yi = y.to_i(2)
z = wires.select { _1.match?(/^z/) }.sort_by(&:first).map { _1.last.to_s }.reverse.join
zi = z.to_i(2)
p zi

p flipped.sort.join(",")

__END__
x00: 0
x01: 1
x02: 0
x03: 1
x04: 0
x05: 1
y00: 0
y01: 0
y02: 1
y03: 1
y04: 0
y05: 1

x00 AND y00 -> z05
x01 AND y01 -> z02
x02 AND y02 -> z01
x03 AND y03 -> z03
x04 AND y04 -> z04
x05 AND y05 -> z00