72 lines
3.6 KiB
Plaintext
72 lines
3.6 KiB
Plaintext
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Advent of Code
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--- Day 5: How About a Nice Game of Chess? ---
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You are faced with a security door designed by Easter Bunny engineers that seem to have acquired most of their security knowledge by watching hacking movies.
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The eight-character password for the door is generated one character at a time by finding the MD5 hash of some Door ID (your puzzle input) and an increasing integer
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index (starting with 0).
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A hash indicates the next character in the password if its hexadecimal representation starts with five zeroes. If it does, the sixth character in the hash is the next
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character of the password.
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For example, if the Door ID is abc:
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• The first index which produces a hash that starts with five zeroes is 3231929, which we find by hashing abc3231929; the sixth character of the hash, and thus the
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first character of the password, is 1.
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• 5017308 produces the next interesting hash, which starts with 000008f82..., so the second character of the password is 8.
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• The third time a hash starts with five zeroes is for abc5278568, discovering the character f.
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In this example, after continuing this search a total of eight times, the password is 18f47a30.
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Given the actual Door ID, what is the password?
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Your puzzle answer was ________.
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--- Part Two ---
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As the door slides open, you are presented with a second door that uses a slightly more inspired security mechanism. Clearly unimpressed by the last version (in what
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movie is the password decrypted in order?!), the Easter Bunny engineers have worked out a better solution.
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Instead of simply filling in the password from left to right, the hash now also indicates the position within the password to fill. You still look for hashes that begin
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with five zeroes; however, now, the sixth character represents the position (0-7), and the seventh character is the character to put in that position.
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A hash result of 000001f means that f is the second character in the password. Use only the first result for each position, and ignore invalid positions.
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For example, if the Door ID is abc:
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• The first interesting hash is from abc3231929, which produces 0000015...; so, 5 goes in position 1: _5______.
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• In the previous method, 5017308 produced an interesting hash; however, it is ignored, because it specifies an invalid position (8).
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• The second interesting hash is at index 5357525, which produces 000004e...; so, e goes in position 4: _5__e___.
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You almost choke on your popcorn as the final character falls into place, producing the password 05ace8e3.
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Given the actual Door ID and this new method, what is the password? Be extra proud of your solution if it uses a cinematic "decrypting" animation.
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Your puzzle answer was ________.
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Your puzzle input was ojvtpuvg.
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References
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Visible links
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. http://adventofcode.com/
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. http://adventofcode.com/2016/about
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. http://adventofcode.com/2016/support
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. http://adventofcode.com/2016/events
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. http://adventofcode.com/2016/settings
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. http://adventofcode.com/2016/auth/logout
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. http://adventofcode.com/2016
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. http://adventofcode.com/2016
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. http://adventofcode.com/2016/leaderboard
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. http://adventofcode.com/2016/stats
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. http://adventofcode.com/2016/sponsors
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. http://adventofcode.com/2016/sponsors
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. https://www.detroitlabs.com/careers
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. https://en.wikipedia.org/wiki/Hackers_(film)
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. https://en.wikipedia.org/wiki/WarGames
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. https://en.wikipedia.org/wiki/MD5
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. https://en.wikipedia.org/wiki/Hexadecimal
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. https://www.youtube.com/watch?v=NHWjlCaIrQo&t=25
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. http://adventofcode.com/2016
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