94 lines
4.2 KiB
Plaintext
94 lines
4.2 KiB
Plaintext
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Advent of Code
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--- Day 23: Safe Cracking ---
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This is one of the top floors of the nicest tower in EBHQ. The Easter Bunny's private office is here, complete with
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a safe hidden behind a painting, and who wouldn't hide a star in a safe behind a painting?
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The safe has a digital screen and keypad for code entry. A sticky note attached to the safe has a password hint on
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it: "eggs". The painting is of a large rabbit coloring some eggs. You see 7.
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When you go to type the code, though, nothing appears on the display; instead, the keypad comes apart in your
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hands, apparently having been smashed. Behind it is some kind of socket - one that matches a connector in your
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prototype computer! You pull apart the smashed keypad and extract the logic circuit, plug it into your computer,
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and plug your computer into the safe.
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Now, you just need to figure out what output the keypad would have sent to the safe. You extract the assembunny
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code from the logic chip (your puzzle input).
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The code looks like it uses almost the same architecture and instruction set that the monorail computer used! You
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should be able to use the same assembunny interpreter for this as you did there, but with one new instruction:
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tgl x toggles the instruction x away (pointing at instructions like jnz does: positive means forward; negative
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means backward):
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• For one-argument instructions, inc becomes dec, and all other one-argument instructions become inc.
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• For two-argument instructions, jnz becomes cpy, and all other two-instructions become jnz.
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• The arguments of a toggled instruction are not affected.
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• If an attempt is made to toggle an instruction outside the program, nothing happens.
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• If toggling produces an invalid instruction (like cpy 1 2) and an attempt is later made to execute that
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instruction, skip it instead.
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• If tgl toggles itself (for example, if a is 0, tgl a would target itself and become inc a), the resulting
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instruction is not executed until the next time it is reached.
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For example, given this program:
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cpy 2 a
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tgl a
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tgl a
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tgl a
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cpy 1 a
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dec a
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dec a
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• cpy 2 a initializes register a to 2.
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• The first tgl a toggles an instruction a (2) away from it, which changes the third tgl a into inc a.
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• The second tgl a also modifies an instruction 2 away from it, which changes the cpy 1 a into jnz 1 a.
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• The fourth line, which is now inc a, increments a to 3.
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• Finally, the fifth line, which is now jnz 1 a, jumps a (3) instructions ahead, skipping the dec a instructions.
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In this example, the final value in register a is 3.
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The rest of the electronics seem to place the keypad entry (the number of eggs, 7) in register a, run the code, and
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then send the value left in register a to the safe.
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What value should be sent to the safe?
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Your puzzle answer was ________.
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--- Part Two ---
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The safe doesn't open, but it does make several angry noises to express its frustration.
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You're quite sure your logic is working correctly, so the only other thing is... you check the painting again. As
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it turns out, colored eggs are still eggs. Now you count 12.
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As you run the program with this new input, the prototype computer begins to overheat. You wonder what's taking so
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long, and whether the lack of any instruction more powerful than "add one" has anything to do with it. Don't
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bunnies usually multiply?
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Anyway, what value should actually be sent to the safe?
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Your puzzle answer was ____________.
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References
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Visible links
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. http://adventofcode.com/
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. http://adventofcode.com/2016/about
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. http://adventofcode.com/2016/support
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. http://adventofcode.com/2016/events
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. http://adventofcode.com/2016/settings
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. http://adventofcode.com/2016/auth/logout
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. http://adventofcode.com/2016
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. http://adventofcode.com/2016
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. http://adventofcode.com/2016/leaderboard
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. http://adventofcode.com/2016/stats
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. http://adventofcode.com/2016/sponsors
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. http://adventofcode.com/2016/sponsors
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. http://adventofcode.com/2016/day/11
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. http://adventofcode.com/2016/day/12
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. http://adventofcode.com/2016/day/12
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. http://adventofcode.com/2016
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. http://adventofcode.com/2016/day/23/input
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