adventofcode/2016/day09/problem

Advent of Code

--- Day 9: Explosives in Cyberspace ---

   Wandering around a secure area, you come across a datalink port to a new
   part of the network. After briefly scanning it for interesting files, you
   find one file in particular that catches your attention. It's compressed
   with an experimental format, but fortunately, the documentation for the
   format is nearby.

   The format compresses a sequence of characters. Whitespace is ignored. To
   indicate that some sequence should be repeated, a marker is added to the
   file, like (10x2). To decompress this marker, take the subsequent 10
   characters and repeat them 2 times. Then, continue reading the file after
   the repeated data. The marker itself is not included in the decompressed
   output.

   If parentheses or other characters appear within the data referenced by a
   marker, that's okay - treat it like normal data, not a marker, and then
   resume looking for markers after the decompressed section.

   For example:

     • ADVENT contains no markers and decompresses to itself with no changes,
     resulting in a decompressed length of 6.

     • A(1x5)BC repeats only the B a total of 5 times, becoming ABBBBBC for a
       decompressed length of 7.

     • (3x3)XYZ becomes XYZXYZXYZ for a decompressed length of 9.

     • A(2x2)BCD(2x2)EFG doubles the BC and EF, becoming ABCBCDEFEFG for a
       decompressed length of 11.

     • (6x1)(1x3)A simply becomes (1x3)A - the (1x3) looks like a marker, but
       because it's within a data section of another marker, it is not treated
       any differently from the A that comes after it. It has a decompressed
       length of 6.

     • X(8x2)(3x3)ABCY becomes X(3x3)ABC(3x3)ABCY (for a decompressed length of
       18), because the decompressed data from the (8x2) marker (the (3x3)ABC) is
       skipped and not processed further.

   What is the decompressed length of the file (your puzzle input)? Don't count
   whitespace.

   Your puzzle answer was 110346.

--- Part Two ---

   Apparently, the file actually uses version two of the format.

   In version two, the only difference is that markers within decompressed data
   are decompressed. This, the documentation explains, provides much more
   substantial compression capabilities, allowing many-gigabyte files to be
   stored in only a few kilobytes.

   For example:

     • (3x3)XYZ still becomes XYZXYZXYZ, as the decompressed section contains
       no markers.

     • X(8x2)(3x3)ABCY becomes XABCABCABCABCABCABCY, because the decompressed
       data from the (8x2) marker is then further decompressed, thus triggering
       the (3x3) marker twice for a total of six ABC sequences.

     • (27x12)(20x12)(13x14)(7x10)(1x12)A decompresses into a string of A
       repeated 241920 times.

     • (25x3)(3x3)ABC(2x3)XY(5x2)PQRSTX(18x9)(3x2)TWO(5x7)SEVEN becomes 445
       characters long.

   Unfortunately, the computer you brought probably doesn't have enough memory
   to actually decompress the file; you'll have to come up with another way to
   get its decompressed length.

   What is the decompressed length of the file using this improved format?

   Although it hasn't changed, you can still get your puzzle input.

   Your puzzle answer was 10774309173.

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