#!/usr/bin/env ruby

require "debug"

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

registers = input[...split]
  .map { _1.split(": ") }
  .map(&:last)
  .map(&:to_i)
  .zip(%i[A B C])
  .map(&:reverse)
  .to_h
program = input[split+1]
  .split(" ")
  .last
  .split(",")
  .map(&:to_i)

OPERANDS = [
  ->() { 0 }, ->() { 1 }, ->() { 2 }, ->() { 3 },
  ->() { registers[:A] },
  ->() { registers[:B] },
  ->() { registers[:C] },
  ->() { :noop },
]

stdout = []

i = 0
while i < program.size
  opcode = program[i]
  literal_operand = program[i+1]
  combo_operand = OPERANDS[literal_operand].call

  i += 2

  case opcode
  when 0
    numerator = registers[:A]
    denominator = 2 ** combo_operand
    registers[:A] = numerator / denominator
  when 1
    registers[:B] = registers[:B] ^ literal_operand
  when 2
    registers[:B] = combo_operand % 8
  when 3
    if registers[:A] == 0
      :noop
    else
      i = literal_operand
    end
  when 4
    registers[:B] = registers[:B] ^ registers[:C]
  when 5
    stdout << combo_operand % 8
  when 6
    numerator = registers[:A]
    denominator = 2 ** combo_operand
    registers[:B] = numerator / denominator
  when 7
    numerator = registers[:A]
    denominator = 2 ** combo_operand
    registers[:C] = numerator / denominator
  end
end

p registers

puts stdout.join(",")

__END__
Register A: 729
Register B: 0
Register C: 0

Program: 0,1,5,4,3,0