79 lines
3.2 KiB
Plaintext
79 lines
3.2 KiB
Plaintext
Advent of Code
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--- Day 12: Leonardo's Monorail ---
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You finally reach the top floor of this building: a garden with a slanted glass ceiling. Looks like there are no more
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stars to be had.
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While sitting on a nearby bench amidst some tiger lilies, you manage to decrypt some of the files you extracted from
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the servers downstairs.
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According to these documents, Easter Bunny HQ isn't just this building - it's a collection of buildings in the nearby
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area. They're all connected by a local monorail, and there's another building not far from here! Unfortunately, being
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night, the monorail is currently not operating.
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You remotely connect to the monorail control systems and discover that the boot sequence expects a password. The
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password-checking logic (your puzzle input) is easy to extract, but the code it uses is strange: it's assembunny code
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designed for the new computer you just assembled. You'll have to execute the code and get the password.
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The assembunny code you've extracted operates on four registers (a, b, c, and d) that start at 0 and can hold any
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integer. However, it seems to make use of only a few instructions:
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• cpy x y copies x (either an integer or the value of a register) into register y.
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• inc x increases the value of register x by one.
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• dec x decreases the value of register x by one.
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• jnz x y jumps to an instruction y away (positive means forward; negative means backward), but only if x is not
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zero.
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The jnz instruction moves relative to itself: an offset of -1 would continue at the previous instruction, while an
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offset of 2 would skip over the next instruction.
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For example:
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cpy 41 a
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inc a
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inc a
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dec a
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jnz a 2
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dec a
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The above code would set register a to 41, increase its value by 2, decrease its value by 1, and then skip the last
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dec a (because a is not zero, so the jnz a 2 skips it), leaving register a at 42. When you move past the last
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instruction, the program halts.
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After executing the assembunny code in your puzzle input, what value is left in register a?
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Your puzzle answer was __________.
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--- Part Two ---
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As you head down the fire escape to the monorail, you notice it didn't start; register c needs to be initialized to
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the position of the ignition key.
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If you instead initialize register c to be 1, what value is now left in register a?
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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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. https://www.google.com/search?q=tiger+lilies&tbm=isch
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. http://adventofcode.com/2016/day/11
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. https://en.wikipedia.org/wiki/Processor_register
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. https://en.wikipedia.org/wiki/Integer
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. https://en.wikipedia.org/wiki/Instruction_set
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. http://adventofcode.com/2016
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. http://adventofcode.com/2016/day/12/input
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