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+<title>Day 24 - Advent of Code 2020</title>
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+Oh, hello! Funny seeing you here.
+
+I appreciate your enthusiasm, but you aren't going to find much down here.
+There certainly aren't clues to any of the puzzles. The best surprises don't
+even appear in the source until you unlock them for real.
+
+Please be careful with automated requests; I'm not a massive company, and I can
+only take so much traffic. Please be considerate so that everyone gets to play.
+
+If you're curious about how Advent of Code works, it's running on some custom
+Perl code. Other than a few integrations (auth, analytics, social media), I
+built the whole thing myself, including the design, animations, prose, and all
+of the puzzles.
+
+The puzzles are most of the work; preparing a new calendar and a new set of
+puzzles each year takes all of my free time for 4-5 months. A lot of effort
+went into building this thing - I hope you're enjoying playing it as much as I
+enjoyed making it for you!
+
+If you'd like to hang out, I'm @ericwastl on Twitter.
+
+- Eric Wastl
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+<header><div><h1 class="title-global"><a href="/">Advent of Code</a></h1><nav><ul><li><a href="/2020/about">[About]</a></li><li><a href="/2020/events">[Events]</a></li><li><a href="https://teespring.com/stores/advent-of-code" target="_blank">[Shop]</a></li><li><a href="/2020/settings">[Settings]</a></li><li><a href="/2020/auth/logout">[Log Out]</a></li></ul></nav><div class="user">Neil Smith <a href="/2020/support" class="supporter-badge" title="Advent of Code Supporter">(AoC++)</a> <span class="star-count">48*</span></div></div><div><h1 class="title-event"> <span class="title-event-wrap">0xffff&</span><a href="/2020">2020</a><span class="title-event-wrap"></span></h1><nav><ul><li><a href="/2020">[Calendar]</a></li><li><a href="/2020/support">[AoC++]</a></li><li><a href="/2020/sponsors">[Sponsors]</a></li><li><a href="/2020/leaderboard">[Leaderboard]</a></li><li><a href="/2020/stats">[Stats]</a></li></ul></nav></div></header>
+
+<div id="sidebar">
+<div id="sponsor"><div class="quiet">Our <a href="/2020/sponsors">sponsors</a> help make Advent of Code possible:</div><div class="sponsor"><a href="https://github.com/" target="_blank" onclick="if(ga)ga('send','event','sponsor','sidebar',this.href);" rel="noopener">GitHub</a> - We're hiring engineers to make GitHub fast. Interested? Email fast@github.com with details of exceptional performance work you've done in the past.</div></div>
+</div><!--/sidebar-->
+
+<main>
+<script>window.addEventListener('click', function(e,s,r){if(e.target.nodeName==='CODE'&&e.detail===3){s=window.getSelection();s.removeAllRanges();r=document.createRange();r.selectNodeContents(e.target);s.addRange(r);}});</script>
+<article class="day-desc"><h2>--- Day 24: Lobby Layout ---</h2><p>Your raft makes it to the tropical island; it turns out that the small crab was an excellent navigator. You make your way to the resort.</p>
+<p>As you enter the lobby, you discover a small problem: the floor is being renovated. You can't even reach the check-in desk until they've finished installing the <em>new tile floor</em>.</p>
+<p>The tiles are all <em>hexagonal</em>; they need to be arranged in a <a href="https://en.wikipedia.org/wiki/Hexagonal_tiling">hex grid</a> with a very specific color pattern. Not in the mood to wait, you offer to help figure out the pattern.</p>
+<p>The tiles are all <em>white</em> on one side and <em>black</em> on the other. They start with the white side facing up. The lobby is large enough to fit whatever pattern might need to appear there.</p>
+<p>A member of the renovation crew gives you a <em>list of the tiles that need to be flipped over</em> (your puzzle input). Each line in the list identifies a single tile that needs to be flipped by giving a series of steps starting from a <em>reference tile</em> in the very center of the room. (Every line starts from the same reference tile.)</p>
+<p>Because the tiles are hexagonal, every tile has <em>six neighbors</em>: east, southeast, southwest, west, northwest, and northeast. These directions are given in your list, respectively, as <code>e</code>, <code>se</code>, <code>sw</code>, <code>w</code>, <code>nw</code>, and <code>ne</code>. A tile is identified by a series of these directions with <em>no delimiters</em>; for example, <code>esenee</code> identifies the tile you land on if you start at the reference tile and then move one tile east, one tile southeast, one tile northeast, and one tile east.</p>
+<p>Each time a tile is identified, it flips from white to black or from black to white. Tiles might be flipped more than once. For example, a line like <code>esew</code> flips a tile immediately adjacent to the reference tile, and a line like <code>nwwswee</code> flips the reference tile itself.</p>
+<p>Here is a larger example:</p>
+<pre><code>sesenwnenenewseeswwswswwnenewsewsw
+neeenesenwnwwswnenewnwwsewnenwseswesw
+seswneswswsenwwnwse
+nwnwneseeswswnenewneswwnewseswneseene
+swweswneswnenwsewnwneneseenw
+eesenwseswswnenwswnwnwsewwnwsene
+sewnenenenesenwsewnenwwwse
+wenwwweseeeweswwwnwwe
+wsweesenenewnwwnwsenewsenwwsesesenwne
+neeswseenwwswnwswswnw
+nenwswwsewswnenenewsenwsenwnesesenew
+enewnwewneswsewnwswenweswnenwsenwsw
+sweneswneswneneenwnewenewwneswswnese
+swwesenesewenwneswnwwneseswwne
+enesenwswwswneneswsenwnewswseenwsese
+wnwnesenesenenwwnenwsewesewsesesew
+nenewswnwewswnenesenwnesewesw
+eneswnwswnwsenenwnwnwwseeswneewsenese
+neswnwewnwnwseenwseesewsenwsweewe
+wseweeenwnesenwwwswnew
+</code></pre>
+<p>In the above example, 10 tiles are flipped once (to black), and 5 more are flipped twice (to black, then back to white). After all of these instructions have been followed, a total of <em><code>10</code></em> tiles are <em>black</em>.</p>
+<p>Go through the renovation crew's list and determine which tiles they need to flip. After all of the instructions have been followed, <em>how many tiles are left with the black side up?</em></p>
+</article>
+<p>Your puzzle answer was <code>538</code>.</p><article class="day-desc"><h2 id="part2">--- Part Two ---</h2><p>The tile floor in the lobby is meant to be a <span title="I need one of these!">living art exhibit</span>. Every day, the tiles are all flipped according to the following rules:</p>
+<ul>
+<li>Any <em>black</em> tile with <em>zero</em> or <em>more than 2</em> black tiles immediately adjacent to it is flipped to <em>white</em>.</li>
+<li>Any <em>white</em> tile with <em>exactly 2</em> black tiles immediately adjacent to it is flipped to <em>black</em>.</li>
+</ul>
+<p>Here, <em>tiles immediately adjacent</em> means the six tiles directly touching the tile in question.</p>
+<p>The rules are applied <em>simultaneously</em> to every tile; put another way, it is first determined which tiles need to be flipped, then they are all flipped at the same time.</p>
+<p>In the above example, the number of black tiles that are facing up after the given number of days has passed is as follows:</p>
+<pre><code>Day 1: 15
+Day 2: 12
+Day 3: 25
+Day 4: 14
+Day 5: 23
+Day 6: 28
+Day 7: 41
+Day 8: 37
+Day 9: 49
+Day 10: 37
+
+Day 20: 132
+Day 30: 259
+Day 40: 406
+Day 50: 566
+Day 60: 788
+Day 70: 1106
+Day 80: 1373
+Day 90: 1844
+Day 100: 2208
+</code></pre>
+<p>After executing this process a total of 100 times, there would be <em><code>2208</code></em> black tiles facing up.</p>
+<p><em>How many tiles will be black after 100 days?</em></p>
+</article>
+<p>Your puzzle answer was <code>4259</code>.</p><p class="day-success">Both parts of this puzzle are complete! They provide two gold stars: **</p>
+<p>At this point, you should <a href="/2020">return to your Advent calendar</a> and try another puzzle.</p>
+<p>If you still want to see it, you can <a href="24/input" target="_blank">get your puzzle input</a>.</p>
+<p>You can also <span class="share">[Share<span class="share-content">on
+ <a href="https://twitter.com/intent/tweet?text=I%27ve+completed+%22Lobby+Layout%22+%2D+Day+24+%2D+Advent+of+Code+2020&url=https%3A%2F%2Fadventofcode%2Ecom%2F2020%2Fday%2F24&related=ericwastl&hashtags=AdventOfCode" target="_blank">Twitter</a>
+ <a href="javascript:void(0);" onclick="var mastodon_instance=prompt('Mastodon Instance / Server Name?'); if(typeof mastodon_instance==='string' && mastodon_instance.length){this.href='https://'+mastodon_instance+'/share?text=I%27ve+completed+%22Lobby+Layout%22+%2D+Day+24+%2D+Advent+of+Code+2020+%23AdventOfCode+https%3A%2F%2Fadventofcode%2Ecom%2F2020%2Fday%2F24'}else{return false;}" target="_blank">Mastodon</a
+></span>]</span> this puzzle.</p>
+</main>
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