205 lines
6.3 KiB
Plaintext
205 lines
6.3 KiB
Plaintext
Advent of Code
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--- Day 10: The Stars Align ---
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It's no use; your navigation system simply isn't capable of providing
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walking directions in the arctic circle, and certainly not in 1018.
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The Elves suggest an alternative. In times like these, North Pole rescue
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operations will arrange points of light in the sky to guide missing Elves
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back to base. Unfortunately, the message is easy to miss: the points move
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slowly enough that it takes hours to align them, but have so much momentum
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that they only stay aligned for a second. If you blink at the wrong time, it
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might be hours before another message appears.
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You can see these points of light floating in the distance, and record their
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position in the sky and their velocity, the relative change in position per
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second (your puzzle input). The coordinates are all given from your
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perspective; given enough time, those positions and velocities will move the
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points into a cohesive message!
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Rather than wait, you decide to fast-forward the process and calculate what
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the points will eventually spell.
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For example, suppose you note the following points:
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position=< 9, 1> velocity=< 0, 2>
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position=< 7, 0> velocity=<-1, 0>
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position=< 3, -2> velocity=<-1, 1>
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position=< 6, 10> velocity=<-2, -1>
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position=< 2, -4> velocity=< 2, 2>
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position=<-6, 10> velocity=< 2, -2>
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position=< 1, 8> velocity=< 1, -1>
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position=< 1, 7> velocity=< 1, 0>
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position=<-3, 11> velocity=< 1, -2>
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position=< 7, 6> velocity=<-1, -1>
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position=<-2, 3> velocity=< 1, 0>
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position=<-4, 3> velocity=< 2, 0>
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position=<10, -3> velocity=<-1, 1>
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position=< 5, 11> velocity=< 1, -2>
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position=< 4, 7> velocity=< 0, -1>
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position=< 8, -2> velocity=< 0, 1>
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position=<15, 0> velocity=<-2, 0>
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position=< 1, 6> velocity=< 1, 0>
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position=< 8, 9> velocity=< 0, -1>
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position=< 3, 3> velocity=<-1, 1>
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position=< 0, 5> velocity=< 0, -1>
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position=<-2, 2> velocity=< 2, 0>
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position=< 5, -2> velocity=< 1, 2>
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position=< 1, 4> velocity=< 2, 1>
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position=<-2, 7> velocity=< 2, -2>
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position=< 3, 6> velocity=<-1, -1>
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position=< 5, 0> velocity=< 1, 0>
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position=<-6, 0> velocity=< 2, 0>
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position=< 5, 9> velocity=< 1, -2>
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position=<14, 7> velocity=<-2, 0>
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position=<-3, 6> velocity=< 2, -1>
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Each line represents one point. Positions are given as <X, Y> pairs: X
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represents how far left (negative) or right (positive) the point appears,
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while Y represents how far up (negative) or down (positive) the point
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appears.
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At 0 seconds, each point has the position given. Each second, each point's
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velocity is added to its position. So, a point with velocity <1, -2> is
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moving to the right, but is moving upward twice as quickly. If this point's
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initial position were <3, 9>, after 3 seconds, its position would become <6,
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3>.
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Over time, the points listed above would move like this:
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Initially:
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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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......#...............
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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 second:
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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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.....##.##..#.........
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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 seconds:
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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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.......#..#..#.#......
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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 seconds:
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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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......#...#...#.......
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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 seconds:
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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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..............#.......
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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 seconds, the message appeared briefly: HI. Of course, your message
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will be much longer and will take many more seconds to appear.
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What message will eventually appear in the sky?
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Your puzzle answer was RECLRNZE.
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--- Part Two ---
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Good thing you didn't have to wait, because that would have taken a long
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time - much longer than the 3 seconds in the example above.
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Impressed by your sub-hour communication capabilities, the Elves are
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curious: exactly how many seconds would they have needed to wait for that
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message to appear?
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Your puzzle answer was 10007.
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Both parts of this puzzle are complete! They provide two gold stars: **
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At this point, you should return to your Advent calendar and try another
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puzzle.
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If you still want to see it, you can get your puzzle input.
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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/10/input
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