Advent of Code

br0xen [7](AoC++) 6*

--- Day 3: Lobby ---

   You descend a short staircase, enter the surprisingly vast lobby, and are
   quickly cleared by the security checkpoint. When you get to the main
   elevators, however, you discover that each one has a red light above it:
   they're all offline.

   "Sorry about that," an Elf apologizes as she tinkers with a nearby control
   panel. "Some kind of electrical surge seems to have fried them. I'll try
   to get them online soon."

   You explain your need to get further underground. "Well, you could at
   least take the escalator down to the printing department, not that you'd
   get much further than that without the elevators working. That is, you
   could if the escalator weren't also offline."

   "But, don't worry! It's not fried; it just needs power. Maybe you can get
   it running while I keep working on the elevators."

   There are batteries nearby that can supply emergency power to the
   escalator for just such an occasion. The batteries are each labeled with
   their [16]joltage rating, a value from 1 to 9. You make a note of their
   joltage ratings (your puzzle input). For example:

 987654321111111
 811111111111119
 234234234234278
 818181911112111

   The batteries are arranged into banks; each line of digits in your input
   corresponds to a single bank of batteries. Within each bank, you need to
   turn on exactly two batteries; the joltage that the bank produces is equal
   to the number formed by the digits on the batteries you've turned on. For
   example, if you have a bank like 12345 and you turn on batteries 2 and 4,
   the bank would produce 24 jolts. (You cannot rearrange batteries.)

   You'll need to find the largest possible joltage each bank can produce. In
   the above example:

     • In 987654321111111, you can make the largest joltage possible, 98, by
       turning on the first two batteries.
     • In 811111111111119, you can make the largest joltage possible by
       turning on the batteries labeled 8 and 9, producing 89 jolts.
     • In 234234234234278, you can make 78 by turning on the last two
       batteries (marked 7 and 8).
     • In 818181911112111, the largest joltage you can produce is 92.

   The total output joltage is the sum of the maximum joltage from each bank,
   so in this example, the total output joltage is 98 + 89 + 78 + 92 = 357.

   There are many batteries in front of you. Find the maximum joltage
   possible from each bank; what is the total output joltage?

   Your puzzle answer was 17113.

--- Part Two ---

   The escalator doesn't move. The Elf explains that it probably needs more
   joltage to overcome the [17]static friction of the system and hits the big
   red "joltage limit safety override" button. You lose count of the number
   of times she needs to confirm "yes, I'm sure" and decorate the lobby a bit
   while you wait.

   Now, you need to make the largest joltage by turning on exactly twelve
   batteries within each bank.

   The joltage output for the bank is still the number formed by the digits
   of the batteries you've turned on; the only difference is that now there
   will be 12 digits in each bank's joltage output instead of two.

   Consider again the example from before:

 987654321111111
 811111111111119
 234234234234278
 818181911112111

   Now, the joltages are much larger:

     • In 987654321111111, the largest joltage can be found by turning on
       everything except some 1s at the end to produce 987654321111.
     • In the digit sequence 811111111111119, the largest joltage can be
       found by turning on everything except some 1s, producing 811111111119.
     • In 234234234234278, the largest joltage can be found by turning on
       everything except a 2 battery, a 3 battery, and another 2 battery near
       the start to produce 434234234278.
     • In 818181911112111, the joltage 888911112111 is produced by turning on
       everything except some 1s near the front.

   The total output joltage is now much larger: 987654321111 + 811111111119 +
   434234234278 + 888911112111 = 3121910778619.

   What is the new total output joltage?

   Your puzzle answer was 169709990062889.

   Both parts of this puzzle are complete! They provide two gold stars: **

   At this point, you should [18]return to your Advent calendar and try
   another puzzle.

   If you still want to see it, you can [19]get your puzzle input.

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