115 lines
4.6 KiB
Plaintext
115 lines
4.6 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
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collecting lumber.
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The lumber collection area is 50 acres by 50 acres; each acre can be either
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open ground (.), trees (|), or a lumberyard (#). You take a scan of the area
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(your puzzle input).
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Strange magic is at work here: each minute, the landscape looks entirely
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different. In exactly one minute, an open acre can fill with trees, a wooded
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acre can be converted to a lumberyard, or a lumberyard can be cleared to
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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
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well as the number of open, wooded, or lumberyard acres adjacent to it at
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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
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might have fewer than eight adjacent acres; the missing acres aren't
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counted.)
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In particular:
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• An open acre will become filled with trees if three or more adjacent
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acres contained trees. Otherwise, nothing happens. • An acre filled with
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trees will become a lumberyard if three or more adjacent acres were
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lumberyards. Otherwise, nothing happens. • An acre containing a lumberyard
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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
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open.
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These changes happen across all acres simultaneously, each of them using the
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state of all acres at the beginning of the minute and changing to their new
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form by the end of that same minute. Changes that happen during the minute
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don't affect each other.
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For example, suppose the lumber collection area is instead only 10 by 10
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acres with this initial configuration:
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Initial state: .#.#...|#. .....#|##| .|..|...#. ..|#.....# #.#|||#|#|
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...#.||... .|....|... ||...#|.#| |.||||..|. ...#.|..|.
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After 1 minute: .......##. ......|### .|..|...#. ..|#||...# ..##||.|#|
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...#||||.. ||...|||.. |||||.||.| |||||||||| ....||..|.
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After 2 minutes: .......#.. ......|#.. .|.|||.... ..##|||..# ..###|||#|
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...#|||||. |||||||||. |||||||||| |||||||||| .|||||||||
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After 3 minutes: .......#.. ....|||#.. .|.||||... ..###|||.# ...##|||#|
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.||##||||| |||||||||| |||||||||| |||||||||| ||||||||||
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After 4 minutes: .....|.#.. ...||||#.. .|.#||||.. ..###||||# ...###||#|
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|||##||||| |||||||||| |||||||||| |||||||||| ||||||||||
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After 5 minutes: ....|||#.. ...||||#.. .|.##||||. ..####|||# .|.###||#|
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|||###|||| |||||||||| |||||||||| |||||||||| ||||||||||
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After 6 minutes: ...||||#.. ...||||#.. .|.###|||. ..#.##|||# |||#.##|#|
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|||###|||| ||||#||||| |||||||||| |||||||||| ||||||||||
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After 7 minutes: ...||||#.. ..||#|##.. .|.####||. ||#..##||# ||##.##|#|
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|||####||| |||###|||| |||||||||| |||||||||| ||||||||||
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After 8 minutes: ..||||##.. ..|#####.. |||#####|. ||#...##|# ||##..###|
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||##.###|| |||####||| ||||#||||| |||||||||| ||||||||||
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After 9 minutes: ..||###... .||#####.. ||##...##. ||#....### |##....##|
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||##..###| ||######|| |||###|||| |||||||||| ||||||||||
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After 10 minutes: .||##..... ||###..... ||##...... |##.....## |##.....##
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|##....##| ||##.####| ||#####||| ||||#||||| ||||||||||
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After 10 minutes, there are 37 wooded acres and 31 lumberyards. Multiplying
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the number of wooded acres by the number of lumberyards gives the total
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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
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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
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years. Are the Elves collecting this lumber sustainably?
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What will the total resource value of the lumber collection area be after
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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/events
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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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