115 lines
4.8 KiB
Plaintext
115 lines
4.8 KiB
Plaintext
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Advent of Code
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--- Day 9: Marble Mania ---
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You talk to the Elves while you wait for your navigation system to
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initialize. To pass the time, they introduce you to their favorite marble
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game.
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The Elves play this game by taking turns arranging the marbles in a
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circle according to very particular rules. The marbles are numbered
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starting with 0 and increasing by 1 until every marble has a number.
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First, the marble numbered 0 is placed in the circle. At this point,
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while it contains only a single marble, it is still a circle: the marble
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is both clockwise from itself and counter-clockwise from itself. This
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marble is designated the current marble.
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Then, each Elf takes a turn placing the lowest-numbered remaining marble
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into the circle between the marbles that are 1 and 2 marbles clockwise of
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the current marble. (When the circle is large enough, this means that
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there is one marble between the marble that was just placed and the
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current marble.) The marble that was just placed then becomes the current
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marble.
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However, if the marble that is about to be placed has a number which is a
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multiple of 23, something entirely different happens. First, the current
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player keeps the marble they would have placed, adding it to their score.
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In addition, the marble 7 marbles counter-clockwise from the current
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marble is removed from the circle and also added to the current player's
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score. The marble located immediately clockwise of the marble that was
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removed becomes the new current marble.
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For example, suppose there are 9 players. After the marble with value 0
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is placed in the middle, each player (shown in square brackets) takes a
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turn. The result of each of those turns would produce circles of marbles
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like this, where clockwise is to the right and the resulting current
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marble is in parentheses:
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[-] (0)
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[1] 0 (1)
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[2] 0 (2) 1
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[3] 0 2 1 (3)
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[4] 0 (4) 2 1 3
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[5] 0 4 2 (5) 1 3
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[6] 0 4 2 5 1 (6) 3
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[7] 0 4 2 5 1 6 3 (7)
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[8] 0 (8) 4 2 5 1 6 3 7
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[9] 0 8 4 (9) 2 5 1 6 3 7
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[1] 0 8 4 9 2(10) 5 1 6 3 7
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[2] 0 8 4 9 2 10 5(11) 1 6 3 7
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[3] 0 8 4 9 2 10 5 11 1(12) 6 3 7
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[4] 0 8 4 9 2 10 5 11 1 12 6(13) 3 7
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[5] 0 8 4 9 2 10 5 11 1 12 6 13 3(14) 7
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[6] 0 8 4 9 2 10 5 11 1 12 6 13 3 14 7(15)
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[7] 0(16) 8 4 9 2 10 5 11 1 12 6 13 3 14 7 15
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[8] 0 16 8(17) 4 9 2 10 5 11 1 12 6 13 3 14 7 15
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[9] 0 16 8 17 4(18) 9 2 10 5 11 1 12 6 13 3 14 7 15
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[1] 0 16 8 17 4 18 9(19) 2 10 5 11 1 12 6 13 3 14 7 15
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[2] 0 16 8 17 4 18 9 19 2(20)10 5 11 1 12 6 13 3 14 7 15
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[3] 0 16 8 17 4 18 9 19 2 20 10(21) 5 11 1 12 6 13 3 14 7 15
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[4] 0 16 8 17 4 18 9 19 2 20 10 21 5(22)11 1 12 6 13 3 14 7 15
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[5] 0 16 8 17 4 18(19) 2 20 10 21 5 22 11 1 12 6 13 3 14 7 15
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[6] 0 16 8 17 4 18 19 2(24)20 10 21 5 22 11 1 12 6 13 3 14 7 15
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[7] 0 16 8 17 4 18 19 2 24 20(25)10 21 5 22 11 1 12 6 13 3 14 7 15
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The goal is to be the player with the highest score after the last marble
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is used up. Assuming the example above ends after the marble numbered 25,
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the winning score is 23+9=32 (because player 5 kept marble 23 and removed
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marble 9, while no other player got any points in this very short example
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game).
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Here are a few more examples:
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* 10 players; last marble is worth 1618 points: high score is 8317
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* 13 players; last marble is worth 7999 points: high score is 146373
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* 17 players; last marble is worth 1104 points: high score is 2764
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* 21 players; last marble is worth 6111 points: high score is 54718
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* 30 players; last marble is worth 5807 points: high score is 37305
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What is the winning Elf's score?
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Your puzzle answer was 394486.
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--- Part Two ---
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Amused by the speed of your answer, the Elves are curious:
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What would the new winning Elf's score be if the number of the last
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marble were 100 times larger?
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Your puzzle answer was 3276488008.
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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://en.wikipedia.org/wiki/Marble_(toy)
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. https://adventofcode.com/2018
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. https://adventofcode.com/2018/day/9/input
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