77 lines
2.7 KiB
Plaintext
77 lines
2.7 KiB
Plaintext
Advent of Code
|
||
|
||
--- Day 4: Security Through Obscurity ---
|
||
|
||
Finally, you come across an information kiosk with a list of rooms. Of
|
||
course, the list is encrypted and full of decoy data, but the instructions
|
||
to decode the list are barely hidden nearby. Better remove the decoy data
|
||
first.
|
||
|
||
Each room consists of an encrypted name (lowercase letters separated by
|
||
dashes) followed by a dash, a sector ID, and a checksum in square brackets.
|
||
|
||
A room is real (not a decoy) if the checksum is the five most common letters
|
||
in the encrypted name, in order, with ties broken by alphabetization. For
|
||
example:
|
||
|
||
• aaaaa-bbb-z-y-x-123[abxyz] is a real room because the most common
|
||
letters are a (5), b (3), and then a tie between x, y, and z, which are
|
||
listed alphabetically.
|
||
|
||
• a-b-c-d-e-f-g-h-987[abcde] is a real room because although the letters
|
||
are all tied (1 of each), the first five are listed alphabetically.
|
||
|
||
• not-a-real-room-404[oarel] is a real room.
|
||
|
||
• totally-real-room-200[decoy] is not.
|
||
|
||
Of the real rooms from the list above, the sum of their sector IDs is 1514.
|
||
|
||
What is the sum of the sector IDs of the real rooms?
|
||
|
||
Your puzzle answer was 245102.
|
||
|
||
The first half of this puzzle is complete! It provides one gold star: *
|
||
|
||
--- Part Two ---
|
||
|
||
With all the decoy data out of the way, it's time to decrypt this list and
|
||
get moving.
|
||
|
||
The room names are encrypted by a state-of-the-art shift cipher, which is
|
||
nearly unbreakable without the right software. However, the information
|
||
kiosk designers at Easter Bunny HQ were not expecting to deal with a master
|
||
cryptographer like yourself.
|
||
|
||
To decrypt a room name, rotate each letter forward through the alphabet a
|
||
number of times equal to the room's sector ID. A becomes B, B becomes C, Z
|
||
becomes A, and so on. Dashes become spaces.
|
||
|
||
For example, the real name for qzmt-zixmtkozy-ivhz-343 is very encrypted
|
||
name.
|
||
|
||
What is the sector ID of the room where North Pole objects are stored?
|
||
|
||
Although it hasn't changed, you can still get your puzzle input.
|
||
|
||
Your puzzle answer was 324.
|
||
|
||
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
|
||
. http://www.novetta.com/careers/#opportunities
|
||
. https://en.wikipedia.org/wiki/Caesar_cipher
|
||
. http://adventofcode.com/2016/day/4/input
|