129 lines
5.1 KiB
Plaintext
129 lines
5.1 KiB
Plaintext
Advent of Code
|
||
|
||
br0xen (AoC++) 16*
|
||
|
||
--- Day 8: Treetop Tree House ---
|
||
|
||
The expedition comes across a peculiar patch of tall trees all planted carefully in a
|
||
grid. The Elves explain that a previous expedition planted these trees as a reforestation
|
||
effort. Now, they're curious if this would be a good location for a tree house.
|
||
|
||
First, determine whether there is enough tree cover here to keep a tree house hidden. To
|
||
do this, you need to count the number of trees that are visible from outside the grid
|
||
when looking directly along a row or column.
|
||
|
||
The Elves have already launched a quadcopter to generate a map with the height of each
|
||
tree (your puzzle input). For example:
|
||
|
||
30373
|
||
25512
|
||
65332
|
||
33549
|
||
35390
|
||
|
||
Each tree is represented as a single digit whose value is its height, where 0 is the
|
||
shortest and 9 is the tallest.
|
||
|
||
A tree is visible if all of the other trees between it and an edge of the grid are
|
||
shorter than it. Only consider trees in the same row or column; that is, only look up,
|
||
down, left, or right from any given tree.
|
||
|
||
All of the trees around the edge of the grid are visible - since they are already on the
|
||
edge, there are no trees to block the view. In this example, that only leaves the
|
||
interior nine trees to consider:
|
||
|
||
• The top-left 5 is visible from the left and top. (It isn't visible from the right or
|
||
bottom since other trees of height 5 are in the way.)
|
||
• The top-middle 5 is visible from the top and right.
|
||
• The top-right 1 is not visible from any direction; for it to be visible, there would
|
||
need to only be trees of height 0 between it and an edge.
|
||
• The left-middle 5 is visible, but only from the right.
|
||
• The center 3 is not visible from any direction; for it to be visible, there would
|
||
need to be only trees of at most height 2 between it and an edge.
|
||
• The right-middle 3 is visible from the right.
|
||
• In the bottom row, the middle 5 is visible, but the 3 and 4 are not.
|
||
|
||
With 16 trees visible on the edge and another 5 visible in the interior, a total of 21
|
||
trees are visible in this arrangement.
|
||
|
||
Consider your map; how many trees are visible from outside the grid?
|
||
|
||
Your puzzle answer was 1693.
|
||
|
||
--- Part Two ---
|
||
|
||
Content with the amount of tree cover available, the Elves just need to know the best
|
||
spot to build their tree house: they would like to be able to see a lot of trees.
|
||
|
||
To measure the viewing distance from a given tree, look up, down, left, and right from
|
||
that tree; stop if you reach an edge or at the first tree that is the same height or
|
||
taller than the tree under consideration. (If a tree is right on the edge, at least one
|
||
of its viewing distances will be zero.)
|
||
|
||
The Elves don't care about distant trees taller than those found by the rules above; the
|
||
proposed tree house has large eaves to keep it dry, so they wouldn't be able to see
|
||
higher than the tree house anyway.
|
||
|
||
In the example above, consider the middle 5 in the second row:
|
||
|
||
30373
|
||
25512
|
||
65332
|
||
33549
|
||
35390
|
||
|
||
• Looking up, its view is not blocked; it can see 1 tree (of height 3).
|
||
• Looking left, its view is blocked immediately; it can see only 1 tree (of height 5,
|
||
right next to it).
|
||
• Looking right, its view is not blocked; it can see 2 trees.
|
||
• Looking down, its view is blocked eventually; it can see 2 trees (one of height 3,
|
||
then the tree of height 5 that blocks its view).
|
||
|
||
A tree's scenic score is found by multiplying together its viewing distance in each of
|
||
the four directions. For this tree, this is 4 (found by multiplying 1 * 1 * 2 * 2).
|
||
|
||
However, you can do even better: consider the tree of height 5 in the middle of the
|
||
fourth row:
|
||
|
||
30373
|
||
25512
|
||
65332
|
||
33549
|
||
35390
|
||
|
||
• Looking up, its view is blocked at 2 trees (by another tree with a height of 5).
|
||
• Looking left, its view is not blocked; it can see 2 trees.
|
||
• Looking down, its view is also not blocked; it can see 1 tree.
|
||
• Looking right, its view is blocked at 2 trees (by a massive tree of height 9).
|
||
|
||
This tree's scenic score is 8 (2 * 2 * 1 * 2); this is the ideal spot for the tree house.
|
||
|
||
Consider each tree on your map. What is the highest scenic score possible for any tree?
|
||
|
||
Your puzzle answer was 422059.
|
||
|
||
Both parts of this puzzle are complete! They provide two gold stars: **
|
||
|
||
References
|
||
|
||
Visible links
|
||
. https://adventofcode.com/
|
||
. https://adventofcode.com/2022/about
|
||
. https://adventofcode.com/2022/events
|
||
. https://adventofcode.com/2022/settings
|
||
. https://adventofcode.com/2022/auth/logout
|
||
. Advent of Code Supporter
|
||
https://adventofcode.com/2022/support
|
||
. https://adventofcode.com/2022
|
||
. https://adventofcode.com/2022
|
||
. https://adventofcode.com/2022/support
|
||
. https://adventofcode.com/2022/sponsors
|
||
. https://adventofcode.com/2022/leaderboard
|
||
. https://adventofcode.com/2022/stats
|
||
. https://adventofcode.com/2022/sponsors
|
||
. https://en.wikipedia.org/wiki/Tree_house
|
||
. https://en.wikipedia.org/wiki/Quadcopter
|
||
. https://en.wikipedia.org/wiki/Eaves
|
||
. https://adventofcode.com/2022
|
||
. https://adventofcode.com/2022/day/8/input
|