2017-12-17 16:00:37 +00:00
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Advent of Code
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--- Day 16: Permutation Promenade ---
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You come upon a very unusual sight; a group of programs here appear to be
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dancing.
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There are sixteen programs in total, named a through p. They start by
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standing in a line: a stands in position 0, b stands in position 1, and so on
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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
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maintain their order otherwise. (For example, s3 on abcde produces
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cdeab).
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* Exchange, written xA/B, makes the programs at positions A and B swap
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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
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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
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input). In what order are the programs standing after their dance?
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2018-03-15 15:08:01 +00:00
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Your puzzle answer was bkgcdefiholnpmja.
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2017-12-17 16:00:37 +00:00
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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
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attention to the dance as a whole.
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Keeping the positions they ended up in from their previous dance, the
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programs perform it again and again: including the first dance, a total of
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one billion (1000000000) times.
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In the example above, their second dance would begin with the order baedc,
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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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2018-03-15 15:08:01 +00:00
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Your puzzle answer was knmdfoijcbpghlea.
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2017-12-17 16:00:37 +00:00
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Both parts of this puzzle are complete! They provide two gold stars: **
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At this point, you should return to your advent calendar and try another
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puzzle.
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If you still want to see it, you can get your puzzle input.
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References
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Visible links
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. http://adventofcode.com/
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. http://adventofcode.com/2017
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. http://adventofcode.com/2017/day/16/input
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