204 lines
4.7 KiB
Plaintext
204 lines
4.7 KiB
Plaintext
Advent of Code
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--- Day 18: Settlers of The North Pole ---
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On the outskirts of the North Pole base construction project, many Elves are collecting lumber.
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The lumber collection area is 50 acres by 50 acres; each acre can be either open ground (.), trees (|), or a
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lumberyard (#). You take a scan of the area (your puzzle input).
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Strange magic is at work here: each minute, the landscape looks entirely different. In exactly one minute, an
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open acre can fill with trees, a wooded acre can be converted to a lumberyard, or a lumberyard can be cleared
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to open ground (the lumber having been sent to other projects).
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The change to each acre is based entirely on the contents of that acre as well as the number of open, wooded,
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or lumberyard acres adjacent to it at the start of each minute. Here, "adjacent" means any of the eight acres
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surrounding that acre. (Acres on the edges of the lumber collection area might have fewer than eight adjacent
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acres; the missing acres aren't counted.)
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In particular:
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• An open acre will become filled with trees if three or more adjacent acres contained trees. Otherwise,
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nothing happens.
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• An acre filled with trees will become a lumberyard if three or more adjacent acres were lumberyards.
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Otherwise, nothing happens.
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• An acre containing a lumberyard will remain a lumberyard if it was adjacent to at least one other
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lumberyard and at least one acre containing trees. Otherwise, it becomes open.
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These changes happen across all acres simultaneously, each of them using the state of all acres at the
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beginning of the minute and changing to their new form by the end of that same minute. Changes that happen
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during the minute don't affect each other.
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For example, suppose the lumber collection area is instead only 10 by 10 acres with this initial
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configuration:
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Initial state:
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.#.#...|#.
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.....#|##|
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.|..|...#.
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..|#.....#
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#.#|||#|#|
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...#.||...
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.|....|...
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||...#|.#|
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...#.|..|.
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After 1 minute:
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.......##.
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......|###
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.|..|...#.
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..|#||...#
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..##||.|#|
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...#||||..
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||...|||..
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|||||.||.|
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....||..|.
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After 2 minutes:
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.......#..
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......|#..
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.|.|||....
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..##|||..#
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..###|||#|
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...#|||||.
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|||||||||.
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.|||||||||
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After 3 minutes:
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.......#..
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....|||#..
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.|.||||...
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..###|||.#
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...##|||#|
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.||##|||||
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After 4 minutes:
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.....|.#..
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...||||#..
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.|.#||||..
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..###||||#
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...###||#|
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After 5 minutes:
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....|||#..
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...||||#..
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.|.##||||.
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..####|||#
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.|.###||#|
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|||###||||
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After 6 minutes:
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...||||#..
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...||||#..
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.|.###|||.
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..#.##|||#
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|||#.##|#|
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||||#|||||
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After 7 minutes:
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...||||#..
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..||#|##..
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.|.####||.
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||#..##||#
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||##.##|#|
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After 8 minutes:
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..||||##..
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..|#####..
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|||#####|.
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||#...##|#
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||##..###|
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||##.###||
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||||#|||||
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After 9 minutes:
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..||###...
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.||#####..
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||##...##.
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||#....###
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|##....##|
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||##..###|
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||######||
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After 10 minutes:
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.||##.....
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||###.....
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||##......
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|##.....##
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|##.....##
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|##....##|
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||##.####|
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||#####|||
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||||#|||||
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After 10 minutes, there are 37 wooded acres and 31 lumberyards. Multiplying the number of wooded acres by the
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number of lumberyards gives the total resource value after ten minutes: 37 * 31 = 1147.
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What will the total resource value of the lumber collection area be after 10 minutes?
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Your puzzle answer was 644640.
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--- Part Two ---
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This important natural resource will need to last for at least thousands of years. Are the Elves collecting
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this lumber sustainably?
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What will the total resource value of the lumber collection area be after 1000000000 minutes?
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Your puzzle answer was 191080.
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Both parts of this puzzle are complete! They provide two gold stars: **
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References
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Visible links
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. https://adventofcode.com/
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. https://adventofcode.com/2018/about
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. https://adventofcode.com/2018/settings
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. https://adventofcode.com/2018/auth/logout
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. Advent of Code Supporter
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https://adventofcode.com/2018/support
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. https://adventofcode.com/2018
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. https://adventofcode.com/2018
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. https://adventofcode.com/2018/support
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. https://adventofcode.com/2018/sponsors
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. https://adventofcode.com/2018/leaderboard
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. https://adventofcode.com/2018/stats
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. https://adventofcode.com/2018/sponsors
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. https://adventofcode.com/2018
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. https://adventofcode.com/2018/day/18/input
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