92 lines
3.2 KiB
Plaintext
92 lines
3.2 KiB
Plaintext
Advent of Code
|
||
|
||
--- Day 12: Leonardo's Monorail ---
|
||
|
||
You finally reach the top floor of this building: a garden with a slanted
|
||
glass ceiling. Looks like there are no more stars to be had.
|
||
|
||
While sitting on a nearby bench amidst some tiger lilies, you manage to
|
||
decrypt some of the files you extracted from the servers downstairs.
|
||
|
||
According to these documents, Easter Bunny HQ isn't just this building -
|
||
it's a collection of buildings in the nearby area. They're all connected by
|
||
a local monorail, and there's another building not far from here!
|
||
Unfortunately, being night, the monorail is currently not operating.
|
||
|
||
You remotely connect to the monorail control systems and discover that the
|
||
boot sequence expects a password. The password-checking logic (your puzzle
|
||
input) is easy to extract, but the code it uses is strange: it's assembunny
|
||
code designed for the new computer you just assembled. You'll have to
|
||
execute the code and get the password.
|
||
|
||
The assembunny code you've extracted operates on four registers (a, b, c,
|
||
and d) that start at 0 and can hold any integer. However, it seems to make
|
||
use of only a few instructions:
|
||
|
||
• cpy x y copies x (either an integer or the value of a register) into
|
||
register y.
|
||
|
||
• inc x increases the value of register x by one.
|
||
|
||
• dec x decreases the value of register x by one.
|
||
|
||
• jnz x y jumps to an instruction y away (positive means forward; negative
|
||
means backward), but only if x is not zero.
|
||
|
||
The jnz instruction moves relative to itself: an offset of -1 would continue
|
||
at the previous instruction, while an offset of 2 would skip over the next
|
||
instruction.
|
||
|
||
For example:
|
||
|
||
cpy 41 a
|
||
inc a
|
||
inc a
|
||
dec a
|
||
jnz a 2
|
||
dec a
|
||
|
||
The above code would set register a to 41, increase its value by 2, decrease
|
||
its value by 1, and then skip the last 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
|
||
instruction, the program halts.
|
||
|
||
After executing the assembunny code in your puzzle input, what value is left
|
||
in register a?
|
||
|
||
Your puzzle answer was 318077.
|
||
|
||
--- Part Two ---
|
||
|
||
As you head down the fire escape to the monorail, you notice it didn't
|
||
start; register c needs to be initialized to the position of the ignition
|
||
key.
|
||
|
||
If you instead initialize register c to be 1, what value is now left in
|
||
register a?
|
||
|
||
Your puzzle answer was 9227731.
|
||
|
||
References
|
||
|
||
Visible links
|
||
. http://adventofcode.com/
|
||
. http://adventofcode.com/2016/about
|
||
. http://adventofcode.com/2016/support
|
||
. http://adventofcode.com/2016/events
|
||
. http://adventofcode.com/2016/settings
|
||
. http://adventofcode.com/2016/auth/logout
|
||
. http://adventofcode.com/2016
|
||
. http://adventofcode.com/2016
|
||
. http://adventofcode.com/2016/leaderboard
|
||
. http://adventofcode.com/2016/stats
|
||
. http://adventofcode.com/2016/sponsors
|
||
. http://adventofcode.com/2016/sponsors
|
||
. https://www.google.com/search?q=tiger+lilies&tbm=isch
|
||
. http://adventofcode.com/2016/day/11
|
||
. https://en.wikipedia.org/wiki/Processor_register
|
||
. https://en.wikipedia.org/wiki/Integer
|
||
. https://en.wikipedia.org/wiki/Instruction_set
|
||
. http://adventofcode.com/2016
|
||
. http://adventofcode.com/2016/day/12/input
|