46 lines
1.6 KiB
Markdown
46 lines
1.6 KiB
Markdown
## \-\-- Day 10: Elves Look, Elves Say \-\--
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Today, the Elves are playing a game called
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[look-and-say](https://en.wikipedia.org/wiki/Look-and-say_sequence).
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They take turns making sequences by reading aloud the previous sequence
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and using that reading as the next sequence. For example, `211` is read
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as \"one two, two ones\", which becomes `1221` (`1` `2`, `2` `1`s).
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Look-and-say sequences are generated iteratively, using the previous
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value as input for the next step. For each step, take the previous
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value, and replace each run of digits (like `111`) with the number of
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digits (`3`) followed by the digit itself (`1`).
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For example:
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- `1` becomes `11` (`1` copy of digit `1`).
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- `11` becomes `21` (`2` copies of digit `1`).
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- `21` becomes `1211` (one `2` followed by one `1`).
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- `1211` becomes `111221` (one `1`, one `2`, and two `1`s).
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- `111221` becomes `312211` (three `1`s, two `2`s, and one `1`).
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Starting with the digits in your puzzle input, apply this process 40
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times. What is *the length of the result*?
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Your puzzle answer was `360154`.
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## \-\-- Part Two \-\-- {#part2}
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Neat, right? You might also enjoy hearing [John Conway talking about
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this sequence](https://www.youtube.com/watch?v=ea7lJkEhytA) (that\'s
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Conway of *Conway\'s Game of Life* fame).
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Now, starting again with the digits in your puzzle input, apply this
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process *50* times. What is *the length of the new result*?
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Your puzzle answer was `5103798`.
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Both parts of this puzzle are complete! They provide two gold stars:
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\*\*
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At this point, you should [return to your Advent calendar](/2015) and
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try another puzzle.
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Your puzzle input was `1113122113`{.puzzle-input}.
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