73 lines
2.4 KiB
Markdown
73 lines
2.4 KiB
Markdown
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## \-\-- Day 7: Recursive Circus \-\--
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Wandering further through the circuits of the computer, you come upon a
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tower of programs that have gotten
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themselves into a bit of trouble. A recursive algorithm has gotten out
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of hand, and now they\'re balanced precariously in a large tower.
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One program at the bottom supports the entire tower. It\'s holding a
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large disc, and on the disc are balanced several more sub-towers. At the
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bottom of these sub-towers, standing on the bottom disc, are other
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programs, each holding *their* own disc, and so on. At the very tops of
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these sub-sub-sub-\...-towers, many programs stand simply keeping the
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disc below them balanced but with no disc of their own.
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You offer to help, but first you need to understand the structure of
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these towers. You ask each program to yell out their *name*, their
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*weight*, and (if they\'re holding a disc) the *names of the programs
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immediately above them* balancing on that disc. You write this
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information down (your puzzle input). Unfortunately, in their panic,
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they don\'t do this in an orderly fashion; by the time you\'re done,
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you\'re not sure which program gave which information.
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For example, if your list is the following:
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pbga (66)
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xhth (57)
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ebii (61)
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havc (66)
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ktlj (57)
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fwft (72) -> ktlj, cntj, xhth
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qoyq (66)
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padx (45) -> pbga, havc, qoyq
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tknk (41) -> ugml, padx, fwft
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jptl (61)
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ugml (68) -> gyxo, ebii, jptl
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gyxo (61)
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cntj (57)
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\...then you would be able to recreate the structure of the towers that
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looks like this:
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gyxo
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/
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ugml - ebii
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/ \
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| jptl
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| pbga
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/ /
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tknk --- padx - havc
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\ \
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| qoyq
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| ktlj
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\ /
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fwft - cntj
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\
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xhth
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In this example, `tknk` is at the bottom of the tower (the *bottom
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program*), and is holding up `ugml`, `padx`, and `fwft`. Those programs
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are, in turn, holding up other programs; in this example, none of those
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programs are holding up any other programs, and are all the tops of
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their own towers. (The actual tower balancing in front of you is much
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larger.)
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Before you\'re ready to help them, you need to make sure your
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information is correct. *What is the name of the bottom program?*
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To begin, [get your puzzle input](7/input).
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Answer:
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