advent-of-code-13.html

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  15 Oh, hello!  Funny seeing you here.
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  17 I appreciate your enthusiasm, but you aren't going to find much down here.
  18 There certainly aren't clues to any of the puzzles.  You do risk spoiling a few
  19 surprises for yourself, though.  Best to play the normal way and discover
  20 everything as it was intended, I think.  The best surprises don't even appear
  21 in the source until you unlock them for real.
  22
  23 Please be careful with automated requests; I'm not Google, and I can only take
  24 so much traffic.  Please be considerate so that everyone gets to play.
  25
  26 If you're curious about how Advent of Code works, it's running on some custom
  27 Perl code. Other than a few integrations (auth, analytics, ads, social media),
  28 I built the whole thing myself, including the design, animations, prose, and
  29 all of the puzzles.
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  31 The puzzles probably took the longest; the easiest ones were around 45 minutes
  32 each, but the harder ones took 2-3 hours, some even longer than that. A lot of
  33 effort went into building this thing - I hope you're enjoying playing it as
  34 much as I enjoyed making it for you!
  35
  36 If you'd like to hang out, I'm @ericwastl on Twitter.
  37
  38 - Eric Wastl
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  90 <body>
  91 <header><h1><a href="/">Advent of Code</a></h1><div class="user">Neil Smith <span class="star-count">26*</span></div><nav><ul><li><a href="/about">[About]</a></li><li><a href="/stats">[Stats]</a></li><li><a href="/leaderboard">[Leaderboard]</a></li><li><a href="/settings">[Settings]</a></li><li><a href="/auth/logout">[Log out]</a></li></ul></nav></header>
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 106 <article class="day-desc"><h2>--- Day 13: Knights of the Dinner Table ---</h2><p>In years past, the holiday feast with your family hasn't gone so well.  Not everyone gets along!  This year, you resolve, will be different.  You're going to find the <em>optimal seating arrangement</em> and avoid all those awkward conversations.</p>
 107 <p>You start by writing up a list of everyone invited and the amount their happiness would increase or decrease if they were to find themselves sitting next to each other person.  You have a circular table that will be just big enough to fit everyone comfortably, and so each person will have exactly two neighbors.</p>
 108 <p>For example, suppose you have only four attendees planned, and you <span title="Finding a method to calculate happiness units is left as an exercise for the reader.">calculate</span> their potential happiness as follows:</p>
 109 <pre><code>Alice would gain 54 happiness units by sitting next to Bob.
 110 Alice would lose 79 happiness units by sitting next to Carol.
 111 Alice would lose 2 happiness units by sitting next to David.
 112 Bob would gain 83 happiness units by sitting next to Alice.
 113 Bob would lose 7 happiness units by sitting next to Carol.
 114 Bob would lose 63 happiness units by sitting next to David.
 115 Carol would lose 62 happiness units by sitting next to Alice.
 116 Carol would gain 60 happiness units by sitting next to Bob.
 117 Carol would gain 55 happiness units by sitting next to David.
 118 David would gain 46 happiness units by sitting next to Alice.
 119 David would lose 7 happiness units by sitting next to Bob.
 120 David would gain 41 happiness units by sitting next to Carol.
 121 </code></pre>
 122 <p>Then, if you seat Alice next to David, Alice would lose <code>2</code> happiness units (because David talks so much), but David would gain <code>46</code> happiness units (because Alice is such a good listener), for a total change of <code>44</code>.</p>
 123 <p>If you continue around the table, you could then seat Bob next to Alice (Bob gains <code>83</code>, Alice gains <code>54</code>).  Finally, seat Carol, who sits next to Bob (Carol gains <code>60</code>, Bob loses <code>7</code>) and David (Carol gains <code>55</code>, David gains <code>41</code>).  The arrangement looks like this:</p>
 124 <pre><code>     +41 +46
 125 +55   David    -2
 126 Carol       Alice
 127 +60    Bob    +54
 128      -7  +83
 129 </code></pre>
 130 <p>After trying every other seating arrangement in this hypothetical scenario, you find that this one is the most optimal, with a total change in happiness of <code>330</code>.</p>
 131 <p>What is the <em>total change in happiness</em> for the optimal seating arrangement of the actual guest list?</p>
 132 </article>
 133 <p>Your puzzle answer was <code>709</code>.</p><article class="day-desc"><h2>--- Part Two ---</h2><p>In all the commotion, you realize that you forgot to seat yourself.  At this point, you're pretty apathetic toward the whole thing, and your happiness wouldn't really go up or down regardless of who you sit next to.  You assume everyone else would be just as ambivalent about sitting next to you, too.</p>
 134 <p>So, add yourself to the list, and give all happiness relationships that involve you a score of <code>0</code>.</p>
 135 <p>What is the <em>total change in happiness</em> for the optimal seating arrangement that actually includes yourself?</p>
 136 </article>
 137 <p>Your puzzle answer was <code>668</code>.</p><p class="day-success">Both parts of this puzzle are complete! They provide two gold stars: **</p>
 138 <p>At this point, you should <a href="/">return to your advent calendar</a> and try another puzzle.</p>
 139 <p>If you still want to see it, you can <a href="/day/13/input" target="_blank">get your puzzle input</a>.</p>
 140 <p>You can also <span class="share">[Share<span class="share-content">on
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 145  this puzzle.</p>
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