Jake Pullen
24 lines
1.8 KiB
Markdown
24 lines
1.8 KiB
Markdown
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<article class="day-desc"><h2>--- Day 18: Boiling Boulders ---</h2><p>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.</p>
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<p>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.</p>
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<p>Depending on the specific compounds in the lava and speed at which it cools, it might be forming <a href="https://en.wikipedia.org/wiki/Obsidian" target="_blank">obsidian</a>! 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).</p>
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<p>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 <em>1x1x1 <span title="Unfortunately, you forgot your flint and steel in another dimension.">cubes</span> on a 3D grid</em>, each given as its <code>x,y,z</code> position.</p>
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<p>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 <code>1,1,1</code> and <code>2,1,1</code>, each cube would have a single side covered and five sides exposed, a total surface area of <code><em>10</em></code> sides.</p>
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<p>Here's a larger example:</p>
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<pre><code>2,2,2
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1,2,2
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3,2,2
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2,1,2
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2,3,2
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2,2,1
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2,2,3
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2,2,4
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2,2,6
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1,2,5
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3,2,5
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2,1,5
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2,3,5
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</code></pre>
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<p>In the above example, after counting up all the sides that aren't connected to another cube, the total surface area is <code><em>64</em></code>.</p>
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<p><em>What is the surface area of your scanned lava droplet?</em></p>
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