2022 Day 18 Complete

2022/day18/problem

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+Advent of Code
+br0xen (AoC++) 35*
+
+--- Day 18: Boiling Boulders ---
+
+   You and the elephants finally reach fresh air. You've emerged near the
+   base of a large volcano that seems to be actively erupting! Fortunately,
+   the lava seems to be flowing away from you and toward the ocean.
+
+   Bits of lava are still being ejected toward you, so you're sheltering in
+   the cavern exit a little longer. Outside the cave, you can see the lava
+   landing in a pond and hear it loudly hissing as it solidifies.
+
+   Depending on the specific compounds in the lava and speed at which it
+   cools, it might be forming obsidian! The cooling rate should be based on
+   the surface area of the lava droplets, so you take a quick scan of a
+   droplet as it flies past you (your puzzle input).
+
+   Because of how quickly the lava is moving, the scan isn't very good; its
+   resolution is quite low and, as a result, it approximates the shape of the
+   lava droplet with 1x1x1 cubes on a 3D grid, each given as its x,y,z
+   position.
+
+   To approximate the surface area, count the number of sides of each cube
+   that are not immediately connected to another cube. So, if your scan were
+   only two adjacent cubes like 1,1,1 and 2,1,1, each cube would have a
+   single side covered and five sides exposed, a total surface area of 10
+   sides.
+
+   Here's a larger example:
+
+ 2,2,2
+ 1,2,2
+ 3,2,2
+ 2,1,2
+ 2,3,2
+ 2,2,1
+ 2,2,3
+ 2,2,4
+ 2,2,6
+ 1,2,5
+ 3,2,5
+ 2,1,5
+ 2,3,5
+
+   In the above example, after counting up all the sides that aren't
+   connected to another cube, the total surface area is 64.
+
+   What is the surface area of your scanned lava droplet?
+
+   Your puzzle answer was 4548.
+
+--- Part Two ---
+
+   Something seems off about your calculation. The cooling rate depends on
+   exterior surface area, but your calculation also included the surface area
+   of air pockets trapped in the lava droplet.
+
+   Instead, consider only cube sides that could be reached by the water and
+   steam as the lava droplet tumbles into the pond. The steam will expand to
+   reach as much as possible, completely displacing any air on the outside of
+   the lava droplet but never expanding diagonally.
+
+   In the larger example above, exactly one cube of air is trapped within the
+   lava droplet (at 2,2,5), so the exterior surface area of the lava droplet
+   is 58.
+
+   What is the exterior surface area of your scanned lava droplet?
+
+   Your puzzle answer was 2588.
+
+   Both parts of this puzzle are complete! They provide two gold stars: **
+
+References
+
+   Visible links
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+   . https://en.wikipedia.org/wiki/Obsidian
+   . https://adventofcode.com/2022
+   . https://adventofcode.com/2022/day/18/input