43 lines
1.9 KiB
Markdown
43 lines
1.9 KiB
Markdown
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# Day 1: Trebuchet?!
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Something is wrong with global snow production, and you've been selected to take a look.
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The Elves have even given you a map; on it, they've used stars to mark the top fifty
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locations that are likely to be having problems.
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You've been doing this long enough to know that to restore snow operations, you need to
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check all *fifty stars* by December 25th.
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Collect stars by solving puzzles. Two puzzles will be made available on each day in
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the Advent calendar; the second puzzle is unlocked when you complete the first. Each
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puzzle grants *one star*. Good luck!
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You try to ask why they can't just use a weather machine ("not powerful enough") and where
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they're even sending you ("the sky") and why your map looks mostly blank ("you sure ask a
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lot of questions") and hang on did you just say the sky ("of course, where do you think
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snow comes from") when you realize that the Elves are already loading you into a
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trebuchet ("please hold still, we need to strap you in").
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As they're making the final adjustments, they discover that their calibration
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document (your puzzle input) has been **amended** by a very young Elf who was apparently
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just excited to show off her art skills. Consequently, the Elves are having trouble
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reading the values on the document.
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The newly-improved calibration document consists of lines of text; each line originally
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contained a specific **calibration value** that the Elves now need to recover. On each line,
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the calibration value can be found by combining the **first digit** and the **last digit**
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(in that order) to form a single **two-digit number**.
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For example:
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```
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1abc2
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pqr3stu8vwx
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a1b2c3d4e5f
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treb7uchet
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```
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In this example, the calibration values of these four lines are 12, 38, 15, and 77.
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Adding these together produces 142.
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Consider your entire calibration document. **What is the sum of all of the calibration values?**
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