+++ /dev/null
---- Day 3: Toboggan Trajectory ---
-With the toboggan login problems resolved, you set off toward the airport. While travel by toboggan might be easy, it's certainly not safe: there's very minimal steering and the area is covered in trees. You'll need to see which angles will take you near the fewest trees.
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-Due to the local geology, trees in this area only grow on exact integer coordinates in a grid. You make a map (your puzzle input) of the open squares (.) and trees (#) you can see. For example:
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-..##.......
-#...#...#..
-.#....#..#.
-..#.#...#.#
-.#...##..#.
-..#.##.....
-.#.#.#....#
-.#........#
-#.##...#...
-#...##....#
-.#..#...#.#
-These aren't the only trees, though; due to something you read about once involving arboreal genetics and biome stability, the same pattern repeats to the right many times:
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-..##.........##.........##.........##.........##.........##....... --->
-#...#...#..#...#...#..#...#...#..#...#...#..#...#...#..#...#...#..
-.#....#..#..#....#..#..#....#..#..#....#..#..#....#..#..#....#..#.
-..#.#...#.#..#.#...#.#..#.#...#.#..#.#...#.#..#.#...#.#..#.#...#.#
-.#...##..#..#...##..#..#...##..#..#...##..#..#...##..#..#...##..#.
-..#.##.......#.##.......#.##.......#.##.......#.##.......#.##..... --->
-.#.#.#....#.#.#.#....#.#.#.#....#.#.#.#....#.#.#.#....#.#.#.#....#
-.#........#.#........#.#........#.#........#.#........#.#........#
-#.##...#...#.##...#...#.##...#...#.##...#...#.##...#...#.##...#...
-#...##....##...##....##...##....##...##....##...##....##...##....#
-.#..#...#.#.#..#...#.#.#..#...#.#.#..#...#.#.#..#...#.#.#..#...#.# --->
-You start on the open square (.) in the top-left corner and need to reach the bottom (below the bottom-most row on your map).
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-The toboggan can only follow a few specific slopes (you opted for a cheaper model that prefers rational numbers); start by counting all the trees you would encounter for the slope right 3, down 1:
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-From your starting position at the top-left, check the position that is right 3 and down 1. Then, check the position that is right 3 and down 1 from there, and so on until you go past the bottom of the map.
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-The locations you'd check in the above example are marked here with O where there was an open square and X where there was a tree:
-
-..##.........##.........##.........##.........##.........##....... --->
-#..O#...#..#...#...#..#...#...#..#...#...#..#...#...#..#...#...#..
-.#....X..#..#....#..#..#....#..#..#....#..#..#....#..#..#....#..#.
-..#.#...#O#..#.#...#.#..#.#...#.#..#.#...#.#..#.#...#.#..#.#...#.#
-.#...##..#..X...##..#..#...##..#..#...##..#..#...##..#..#...##..#.
-..#.##.......#.X#.......#.##.......#.##.......#.##.......#.##..... --->
-.#.#.#....#.#.#.#.O..#.#.#.#....#.#.#.#....#.#.#.#....#.#.#.#....#
-.#........#.#........X.#........#.#........#.#........#.#........#
-#.##...#...#.##...#...#.X#...#...#.##...#...#.##...#...#.##...#...
-#...##....##...##....##...#X....##...##....##...##....##...##....#
-.#..#...#.#.#..#...#.#.#..#...X.#.#..#...#.#.#..#...#.#.#..#...#.# --->
-In this example, traversing the map using this slope would cause you to encounter 7 trees.
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-Starting at the top-left corner of your map and following a slope of right 3 and down 1, how many trees would you encounter?
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-Your puzzle answer was 234.
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---- Part Two ---
-Time to check the rest of the slopes - you need to minimize the probability of a sudden arboreal stop, after all.
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-Determine the number of trees you would encounter if, for each of the following slopes, you start at the top-left corner and traverse the map all the way to the bottom:
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-Right 1, down 1.
-Right 3, down 1. (This is the slope you already checked.)
-Right 5, down 1.
-Right 7, down 1.
-Right 1, down 2.
-In the above example, these slopes would find 2, 7, 3, 4, and 2 tree(s) respectively; multiplied together, these produce the answer 336.
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-What do you get if you multiply together the number of trees encountered on each of the listed slopes?
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-Your puzzle answer was 5813773056.
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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 puzzle.
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-If you still want to see it, you can get your puzzle input.
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-You can also [Share] this puzzle.
projects / advent-of-code-2020.git / blobdiff