47 lines
No EOL
2.1 KiB
Text
47 lines
No EOL
2.1 KiB
Text
\--- Day 16: Permutation Promenade ---
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You come upon a very unusual sight; a group of programs here appear to be [dancing](https://www.youtube.com/watch?v=lyZQPjUT5B4&t=53).
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There are sixteen programs in total, named `a` through `p`. They start by standing in a line: `a` stands in position `0`, `b` stands in position `1`, and so on until `p`, which stands in position `15`.
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The programs' *dance* consists of a sequence of *dance moves*:
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* *Spin*, written `sX`, makes `X` programs move from the end to the front, but maintain their order otherwise. (For example, `s3` on `abcde` produces `cdeab`).
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* *Exchange*, written `xA/B`, makes the programs at positions `A` and `B` swap places.
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* *Partner*, written `pA/B`, makes the programs named `A` and `B` swap places.
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For example, with only five programs standing in a line (`abcde`), they could do the following dance:
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* `s1`, a spin of size `1`: `eabcd`.
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* `x3/4`, swapping the last two programs: `eabdc`.
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* `pe/b`, swapping programs `e` and `b`: `baedc`.
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After finishing their dance, the programs end up in order `baedc`.
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You watch the dance for a while and record their dance moves (your puzzle input). *In what order are the programs standing* after their dance?
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Your puzzle answer was `cgpfhdnambekjiol`.
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\--- Part Two ---
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Now that you're starting to get a feel for the dance moves, you turn your attention to *the dance as a whole*.
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Keeping the positions they ended up in from their previous dance, the programs perform it again and again: including the first dance, a total of *one billion* (`1000000000`) times.
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In the example above, their second dance would *begin* with the order `baedc`, and use the same dance moves:
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* `s1`, a spin of size `1`: `cbaed`.
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* `x3/4`, swapping the last two programs: `cbade`.
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* `pe/b`, swapping programs `e` and `b`: `ceadb`.
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*In what order are the programs standing* after their billion dances?
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Your puzzle answer was `gjmiofcnaehpdlbk`.
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Both parts of this puzzle are complete! They provide two gold stars: \*\*
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At this point, all that is left is for you to [admire your Advent calendar](/2017).
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If you still want to see it, you can [get your puzzle input](16/input). |