2017-12-01 12:41:19 +00:00
|
|
|
|
Advent of Code
|
|
|
|
|
|
|
|
|
|
|
|
--- Day 1: Inverse Captcha ---
|
|
|
|
|
|
|
2018-03-15 15:08:01 +00:00
|
|
|
|
The night before Christmas, one of Santa's Elves calls you in a panic. "The
|
|
|
|
|
|
printer's broken! We can't print the Naughty or Nice List!" By the time you
|
|
|
|
|
|
make it to sub-basement 17, there are only a few minutes until midnight. "We
|
|
|
|
|
|
have a big problem," she says; "there must be almost fifty bugs in this
|
|
|
|
|
|
system, but nothing else can print The List. Stand in this square, quick!
|
|
|
|
|
|
There's no time to explain; if you can convince them to pay you in stars,
|
|
|
|
|
|
you'll be able to--" She pulls a lever and the world goes blurry.
|
|
|
|
|
|
|
|
|
|
|
|
When your eyes can focus again, everything seems a lot more pixelated than
|
|
|
|
|
|
before. She must have sent you inside the computer! You check the system
|
|
|
|
|
|
clock: 25 milliseconds until midnight. With that much time, you should be
|
|
|
|
|
|
able to collect all fifty stars by December 25th.
|
|
|
|
|
|
|
|
|
|
|
|
Collect stars by solving puzzles. Two puzzles will be made available on each
|
|
|
|
|
|
day millisecond in the advent calendar; the second puzzle is unlocked when
|
|
|
|
|
|
you complete the first. Each puzzle grants one star. Good luck!
|
|
|
|
|
|
|
|
|
|
|
|
You're standing in a room with "digitization quarantine" written in LEDs
|
|
|
|
|
|
along one wall. The only door is locked, but it includes a small interface.
|
|
|
|
|
|
"Restricted Area - Strictly No Digitized Users Allowed."
|
|
|
|
|
|
|
|
|
|
|
|
It goes on to explain that you may only leave by solving a captcha to prove
|
|
|
|
|
|
you're not a human. Apparently, you only get one millisecond to solve the
|
|
|
|
|
|
captcha: too fast for a normal human, but it feels like hours to you.
|
|
|
|
|
|
|
|
|
|
|
|
The captcha requires you to review a sequence of digits (your puzzle input)
|
|
|
|
|
|
and find the sum of all digits that match the next digit in the list. The
|
|
|
|
|
|
list is circular, so the digit after the last digit is the first digit in
|
|
|
|
|
|
the list.
|
2017-12-01 12:41:19 +00:00
|
|
|
|
|
|
|
|
|
|
For example:
|
|
|
|
|
|
|
2018-03-15 15:08:01 +00:00
|
|
|
|
• 1122 produces a sum of 3 (1 + 2) because the first digit (1) matches the
|
|
|
|
|
|
second digit and the third digit (2) matches the fourth digit.
|
|
|
|
|
|
• 1111 produces 4 because each digit (all 1) matches the next.
|
2017-12-01 12:41:19 +00:00
|
|
|
|
• 1234 produces 0 because no digit matches the next.
|
2018-03-15 15:08:01 +00:00
|
|
|
|
• 91212129 produces 9 because the only digit that matches the next one is
|
|
|
|
|
|
the last digit, 9.
|
2017-12-01 12:41:19 +00:00
|
|
|
|
|
|
|
|
|
|
What is the solution to your captcha?
|
|
|
|
|
|
|
2018-03-15 15:08:01 +00:00
|
|
|
|
Your puzzle answer was 1144.
|
2017-12-01 12:41:19 +00:00
|
|
|
|
|
|
|
|
|
|
--- Part Two ---
|
|
|
|
|
|
|
2018-03-15 15:08:01 +00:00
|
|
|
|
You notice a progress bar that jumps to 50% completion. Apparently, the door
|
|
|
|
|
|
isn't yet satisfied, but it did emit a star as encouragement. The
|
|
|
|
|
|
instructions change:
|
2017-12-01 12:41:19 +00:00
|
|
|
|
|
2018-03-15 15:08:01 +00:00
|
|
|
|
Now, instead of considering the next digit, it wants you to consider the
|
|
|
|
|
|
digit halfway around the circular list. That is, if your list contains 10
|
|
|
|
|
|
items, only include a digit in your sum if the digit 10/2 = 5 steps forward
|
|
|
|
|
|
matches it. Fortunately, your list has an even number of elements.
|
2017-12-01 12:41:19 +00:00
|
|
|
|
|
|
|
|
|
|
For example:
|
|
|
|
|
|
|
2018-03-15 15:08:01 +00:00
|
|
|
|
• 1212 produces 6: the list contains 4 items, and all four digits match
|
|
|
|
|
|
the digit 2 items ahead.
|
2017-12-01 12:41:19 +00:00
|
|
|
|
• 1221 produces 0, because every comparison is between a 1 and a 2.
|
2018-03-15 15:08:01 +00:00
|
|
|
|
• 123425 produces 4, because both 2s match each other, but no other digit
|
|
|
|
|
|
has a match.
|
2017-12-01 12:41:19 +00:00
|
|
|
|
• 123123 produces 12.
|
|
|
|
|
|
• 12131415 produces 4.
|
|
|
|
|
|
|
|
|
|
|
|
What is the solution to your new captcha?
|
|
|
|
|
|
|
2018-03-15 15:08:01 +00:00
|
|
|
|
Your puzzle answer was 1194.
|
2017-12-01 12:41:19 +00:00
|
|
|
|
|
|
|
|
|
|
Both parts of this puzzle are complete! They provide two gold stars: **
|
|
|
|
|
|
|
2018-03-15 15:08:01 +00:00
|
|
|
|
At this point, you should return to your advent calendar and try another
|
|
|
|
|
|
puzzle.
|
2017-12-01 12:41:19 +00:00
|
|
|
|
|
|
|
|
|
|
If you still want to see it, you can get your puzzle input.
|
|
|
|
|
|
|
|
|
|
|
|
References
|
|
|
|
|
|
|
|
|
|
|
|
Visible links
|
|
|
|
|
|
. http://adventofcode.com/
|
|
|
|
|
|
. http://adventofcode.com/2017/about
|
|
|
|
|
|
. http://adventofcode.com/2017/support
|
|
|
|
|
|
. http://adventofcode.com/2017/events
|
|
|
|
|
|
. http://adventofcode.com/2017/settings
|
|
|
|
|
|
. http://adventofcode.com/2017/auth/logout
|
|
|
|
|
|
. http://adventofcode.com/2017
|
|
|
|
|
|
. http://adventofcode.com/2017
|
|
|
|
|
|
. http://adventofcode.com/2017/leaderboard
|
|
|
|
|
|
. http://adventofcode.com/2017/stats
|
|
|
|
|
|
. http://adventofcode.com/2017/sponsors
|
|
|
|
|
|
. http://adventofcode.com/2017/sponsors
|
|
|
|
|
|
. https://en.wikipedia.org/wiki/CAPTCHA
|
|
|
|
|
|
. http://adventofcode.com/2017
|
|
|
|
|
|
. http://adventofcode.com/2017/day/1/input
|
