120 lines
4.9 KiB
Plaintext
120 lines
4.9 KiB
Plaintext
|
# Advent of Code
|
|||
|
|
|
|||
|
|
--- 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.
|
|||
|
|
|
|||
|
|
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:
|
|||
|
|
|
|||
|
|
..##.......
|
|||
|
|
#...#...#..
|
|||
|
|
.#....#..#.
|
|||
|
|
..#.#...#.#
|
|||
|
|
.#...##..#.
|
|||
|
|
..#.##.....
|
|||
|
|
.#.#.#....#
|
|||
|
|
.#........#
|
|||
|
|
#.##...#...
|
|||
|
|
#...##....#
|
|||
|
|
.#..#...#.#
|
|||
|
|
|
|||
|
|
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:
|
|||
|
|
|
|||
|
|
..##.........##.........##.........##.........##.........##....... --->
|
|||
|
|
#...#...#..#...#...#..#...#...#..#...#...#..#...#...#..#...#...#..
|
|||
|
|
.#....#..#..#....#..#..#....#..#..#....#..#..#....#..#..#....#..#.
|
|||
|
|
..#.#...#.#..#.#...#.#..#.#...#.#..#.#...#.#..#.#...#.#..#.#...#.#
|
|||
|
|
.#...##..#..#...##..#..#...##..#..#...##..#..#...##..#..#...##..#.
|
|||
|
|
..#.##.......#.##.......#.##.......#.##.......#.##.......#.##..... --->
|
|||
|
|
.#.#.#....#.#.#.#....#.#.#.#....#.#.#.#....#.#.#.#....#.#.#.#....#
|
|||
|
|
.#........#.#........#.#........#.#........#.#........#.#........#
|
|||
|
|
#.##...#...#.##...#...#.##...#...#.##...#...#.##...#...#.##...#...
|
|||
|
|
#...##....##...##....##...##....##...##....##...##....##...##....#
|
|||
|
|
.#..#...#.#.#..#...#.#.#..#...#.#.#..#...#.#.#..#...#.#.#..#...#.# --->
|
|||
|
|
|
|||
|
|
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).
|
|||
|
|
|
|||
|
|
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:
|
|||
|
|
|
|||
|
|
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.
|
|||
|
|
|
|||
|
|
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.
|
|||
|
|
|
|||
|
|
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?
|
|||
|
|
|
|||
|
|
Your puzzle answer was 289.
|
|||
|
|
|
|||
|
|
--- Part Two ---
|
|||
|
|
|
|||
|
|
Time to check the rest of the slopes - you need to minimize the probability of a sudden
|
|||
|
|
arboreal stop, after all.
|
|||
|
|
|
|||
|
|
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:
|
|||
|
|
|
|||
|
|
• 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.
|
|||
|
|
|
|||
|
|
What do you get if you multiply together the number of trees encountered on each of the
|
|||
|
|
listed slopes?
|
|||
|
|
|
|||
|
|
Your puzzle answer was 5522401584.
|
|||
|
|
|
|||
|
|
Both parts of this puzzle are complete! They provide two gold stars: **
|
|||
|
|
|
|||
|
|
At this point, you should return to your Advent calendar and try another puzzle.
|
|||
|
|
|
|||
|
|
If you still want to see it, you can get your puzzle input.
|
|||
|
|
|
|||
|
|
References
|
|||
|
|
|
|||
|
|
Visible links
|
|||
|
|
. https://adventofcode.com/
|
|||
|
|
. https://adventofcode.com/2020/about
|
|||
|
|
. https://adventofcode.com/2020/events
|
|||
|
|
. https://adventofcode.com/2020/settings
|
|||
|
|
. https://adventofcode.com/2020/auth/logout
|
|||
|
|
. Advent of Code Supporter
|
|||
|
|
https://adventofcode.com/2020/support
|
|||
|
|
. https://adventofcode.com/2020
|
|||
|
|
. https://adventofcode.com/2020
|
|||
|
|
. https://adventofcode.com/2020/support
|
|||
|
|
. https://adventofcode.com/2020/sponsors
|
|||
|
|
. https://adventofcode.com/2020/leaderboard
|
|||
|
|
. https://adventofcode.com/2020/stats
|
|||
|
|
. https://adventofcode.com/2020/sponsors
|
|||
|
|
. https://adventofcode.com/2020
|
|||
|
|
. https://adventofcode.com/2020/day/3/input
|