124 lines
2.8 KiB
Ruby
Executable file
124 lines
2.8 KiB
Ruby
Executable file
#!/usr/bin/env ruby
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require "debug"
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DEBUG = false
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input = (ARGV.first.nil? ? DATA : ARGF)
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.readlines(chomp: true)
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split = input.index("")
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registers = input[...split]
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.map { _1.split(": ") }
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.map(&:last)
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.map(&:to_i)
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.zip(%i[A B C])
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.map(&:reverse)
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.to_h
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program = input[split+1]
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.split(" ")
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.last
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.split(",")
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.map(&:to_i)
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def execute(registers, program)
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stdout, commands = Array.new, Array.new
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operands = [
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->() { 0 }, ->() { 1 }, ->() { 2 }, ->() { 3 },
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->() { registers[:A] },
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->() { registers[:B] },
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->() { registers[:C] },
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->() { :noop },
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]
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ic = 0
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while ic < program.size
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opcode = program[ic]
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literal_operand = program[ic+1]
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combo_operand = operands[literal_operand].call
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ic += 2
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case opcode
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when 0
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numerator = registers[:A]
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denominator = 2 ** combo_operand
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registers[:A] = numerator / denominator
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commands << [:adv, numerator, denominator]
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when 1
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registers[:B] = registers[:B] ^ literal_operand
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commands << [:bxl, literal_operand]
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when 2
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registers[:B] = combo_operand % 8
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commands << [:bst, combo_operand % 8]
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when 3
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if registers[:A] == 0
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commands << [:noop]
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else
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ic = literal_operand
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commands << [:jnz, literal_operand]
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end
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when 4
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registers[:B] = registers[:B] ^ registers[:C]
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commands << [:bxc, registers[:B], registers[:C]]
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when 5
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stdout << combo_operand % 8
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commands << [:out, combo_operand % 8]
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when 6
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numerator = registers[:A]
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denominator = 2 ** combo_operand
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registers[:B] = numerator / denominator
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commands << [:bdv, numerator, denominator]
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when 7
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numerator = registers[:A]
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denominator = 2 ** combo_operand
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registers[:C] = numerator / denominator
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commands << [:cdv, numerator, denominator]
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end
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end
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if DEBUG
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commands.each { puts _1.join(" ") }
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end
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[registers, program, stdout.join(",")]
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end
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_, _, part_1 = execute(registers.dup, program)
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p part_1
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def reverse_engineer(program, slot, i)
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candidates = (0..8).map do |i|
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[i, execute({A: i, B: 0, C: 0}, program).last.split(",").map(&:to_i)
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]
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end.select { _1.last == program[slot..] }
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end
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part_2 = 0
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(program.size - 1).downto(0) do |slot|
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candidates = []
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(0..8).each do |i|
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candidate = part_2 + i
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_, _, output = execute({A: candidate, B: 0, C: 0}, program)
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new_program = output.split(",").map(&:to_i)
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if new_program == program[slot..]
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candidates << candidate
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unless [301,2566855701950, 20534845615581, 20534845615573, 20534845615583].include?(candidate)
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part_2 = candidate
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end
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end
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end
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#p candidates
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if slot == 0
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p candidates.first
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end
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part_2 <<= 3
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end
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__END__
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Register A: 2024
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Register B: 0
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Register C: 0
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Program: 0,3,5,4,3,0
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