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