79 lines
3.2 KiB
Plaintext
79 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 __________.
|
|||
|
|
|||
|
--- 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 ___________.
|
|||
|
|
|||
|
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
|