70 lines
2.8 KiB
Plaintext
70 lines
2.8 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 ___________.
|
|||
|
|
|
|||
|
|
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.
|
|||
|
|
|
|||
|
|
Answer: _____________________ [ [Submit] ]
|
|||
|
|
|
|||
|
|
You can also [Shareon Twitter Google+ Reddit] this puzzle.
|
|||
|
|
|
|||
|
|
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
|