problems/day14.html

   1 <!DOCTYPE html>
   2 <html lang="en-us">
   3 <head>
   4 <meta charset="utf-8"/>
   5 <title>Day 14 - Advent of Code 2021</title>
   6 <!--[if lt IE 9]><script src="/static/html5.js"></script><![endif]-->
   7 <link href='//fonts.googleapis.com/css?family=Source+Code+Pro:300&subset=latin,latin-ext' rel='stylesheet' type='text/css'/>
   8 <link rel="stylesheet" type="text/css" href="/static/style.css?26"/>
   9 <link rel="stylesheet alternate" type="text/css" href="/static/highcontrast.css?0" title="High Contrast"/>
  10 <link rel="shortcut icon" href="/favicon.png"/>
  11 </head><!--
  12
  13
  14
  15
  16 Oh, hello!  Funny seeing you here.
  17
  18 I appreciate your enthusiasm, but you aren't going to find much down here.
  19 There certainly aren't clues to any of the puzzles.  The best surprises don't
  20 even appear in the source until you unlock them for real.
  21
  22 Please be careful with automated requests; I'm not a massive company, and I can
  23 only take so much traffic.  Please be considerate so that everyone gets to play.
  24
  25 If you're curious about how Advent of Code works, it's running on some custom
  26 Perl code. Other than a few integrations (auth, analytics, social media), I
  27 built the whole thing myself, including the design, animations, prose, and all
  28 of the puzzles.
  29
  30 The puzzles are most of the work; preparing a new calendar and a new set of
  31 puzzles each year takes all of my free time for 4-5 months. A lot of effort
  32 went into building this thing - I hope you're enjoying playing it as much as I
  33 enjoyed making it for you!
  34
  35 If you'd like to hang out, I'm @ericwastl on Twitter.
  36
  37 - Eric Wastl
  38
  39
  40
  41
  42
  43
  44
  45
  46
  47
  48
  49
  50
  51
  52
  53
  54
  55
  56
  57
  58
  59
  60
  61
  62
  63
  64
  65
  66
  67
  68
  69
  70
  71
  72
  73
  74
  75
  76
  77
  78
  79
  80
  81
  82
  83
  84
  85
  86
  87
  88 -->
  89 <body>
  90 <header><div><h1 class="title-global"><a href="/">Advent of Code</a></h1><nav><ul><li><a href="/2021/about">[About]</a></li><li><a href="/2021/events">[Events]</a></li><li><a href="https://teespring.com/stores/advent-of-code" target="_blank">[Shop]</a></li><li><a href="/2021/settings">[Settings]</a></li><li><a href="/2021/auth/logout">[Log Out]</a></li></ul></nav><div class="user">Neil Smith <a href="/2021/support" class="supporter-badge" title="Advent of Code Supporter">(AoC++)</a> <span class="star-count">30*</span></div></div><div><h1 class="title-event">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span class="title-event-wrap"></span><a href="/2021">2021</a><span class="title-event-wrap"></span></h1><nav><ul><li><a href="/2021">[Calendar]</a></li><li><a href="/2021/support">[AoC++]</a></li><li><a href="/2021/sponsors">[Sponsors]</a></li><li><a href="/2021/leaderboard">[Leaderboard]</a></li><li><a href="/2021/stats">[Stats]</a></li></ul></nav></div></header>
  91
  92 <div id="sidebar">
  93 <div id="sponsor"><div class="quiet">Our <a href="/2021/sponsors">sponsors</a> help make Advent of Code possible:</div><div class="sponsor"><a href="https://www.tcgplayer.com/adventofcode/?utm_campaign=aoc&amp;utm_source=adventOfCode&amp;utm_medium=aocPromo" target="_blank" onclick="if(ga)ga('send','event','sponsor','sidebar',this.href);" rel="noopener">TCGplayer.com</a> - - . Hiring .NET &amp; . . JS engineers. . . Help us serve . . our community . . of game stores. . &amp; hobbyists!! . ---- JOIN US ----</div></div>
  94 </div><!--/sidebar-->
  95
  96 <main>
  97 <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>
  98 <article class="day-desc"><h2>--- Day 14: Extended Polymerization ---</h2><p>The incredible pressures at this depth are starting to put a strain on your submarine. The submarine has <a href="https://en.wikipedia.org/wiki/Polymerization" target="_blank">polymerization</a> equipment that would produce suitable materials to reinforce the submarine, and the nearby volcanically-active caves should even have the necessary input elements in sufficient quantities.</p>
  99 <p>The submarine manual contains <span title="HO&#xa;&#xa;HO -&gt; OH">instructions</span> for finding the optimal polymer formula; specifically, it offers a <em>polymer template</em> and a list of <em>pair insertion</em> rules (your puzzle input). You just need to work out what polymer would result after repeating the pair insertion process a few times.</p>
 100 <p>For example:</p>
 101 <pre><code>NNCB
 102
 103 CH -&gt; B
 104 HH -&gt; N
 105 CB -&gt; H
 106 NH -&gt; C
 107 HB -&gt; C
 108 HC -&gt; B
 109 HN -&gt; C
 110 NN -&gt; C
 111 BH -&gt; H
 112 NC -&gt; B
 113 NB -&gt; B
 114 BN -&gt; B
 115 BB -&gt; N
 116 BC -&gt; B
 117 CC -&gt; N
 118 CN -&gt; C
 119 </code></pre>
 120 <p>The first line is the <em>polymer template</em> - this is the starting point of the process.</p>
 121 <p>The following section defines the <em>pair insertion</em> rules. A rule like <code>AB -&gt; C</code> means that when elements <code>A</code> and <code>B</code> are immediately adjacent, element <code>C</code> should be inserted between them. These insertions all happen simultaneously.</p>
 122 <p>So, starting with the polymer template <code>NNCB</code>, the first step simultaneously considers all three pairs:</p>
 123 <ul>
 124 <li>The first pair (<code>NN</code>) matches the rule <code>NN -&gt; C</code>, so element <code><em>C</em></code> is inserted between the first <code>N</code> and the second <code>N</code>.</li>
 125 <li>The second pair (<code>NC</code>) matches the rule <code>NC -&gt; B</code>, so element <code><em>B</em></code> is inserted between the <code>N</code> and the <code>C</code>.</li>
 126 <li>The third pair (<code>CB</code>) matches the rule <code>CB -&gt; H</code>, so element <code><em>H</em></code> is inserted between the <code>C</code> and the <code>B</code>.</li>
 127 </ul>
 128 <p>Note that these pairs overlap: the second element of one pair is the first element of the next pair. Also, because all pairs are considered simultaneously, inserted elements are not considered to be part of a pair until the next step.</p>
 129 <p>After the first step of this process, the polymer becomes <code>N<em>C</em>N<em>B</em>C<em>H</em>B</code>.</p>
 130 <p>Here are the results of a few steps using the above rules:</p>
 131 <pre><code>Template:     NNCB
 132 After step 1: NCNBCHB
 133 After step 2: NBCCNBBBCBHCB
 134 After step 3: NBBBCNCCNBBNBNBBCHBHHBCHB
 135 After step 4: NBBNBNBBCCNBCNCCNBBNBBNBBBNBBNBBCBHCBHHNHCBBCBHCB
 136 </code></pre>
 137 <p>This polymer grows quickly. After step 5, it has length 97; After step 10, it has length 3073. After step 10, <code>B</code> occurs 1749 times, <code>C</code> occurs 298 times, <code>H</code> occurs 161 times, and <code>N</code> occurs 865 times; taking the quantity of the most common element (<code>B</code>, 1749) and subtracting the quantity of the least common element (<code>H</code>, 161) produces <code>1749 - 161 = <em>1588</em></code>.</p>
 138 <p>Apply 10 steps of pair insertion to the polymer template and find the most and least common elements in the result. <em>What do you get if you take the quantity of the most common element and subtract the quantity of the least common element?</em></p>
 139 </article>
 140 <p>Your puzzle answer was <code>2712</code>.</p><article class="day-desc"><h2 id="part2">--- Part Two ---</h2><p>The resulting polymer isn't nearly strong enough to reinforce the submarine. You'll need to run more steps of the pair insertion process; a total of <em>40 steps</em> should do it.</p>
 141 <p>In the above example, the most common element is <code>B</code> (occurring <code>2192039569602</code> times) and the least common element is <code>H</code> (occurring <code>3849876073</code> times); subtracting these produces <code><em>2188189693529</em></code>.</p>
 142 <p>Apply <em>40</em> steps of pair insertion to the polymer template and find the most and least common elements in the result. <em>What do you get if you take the quantity of the most common element and subtract the quantity of the least common element?</em></p>
 143 </article>
 144 <p>Your puzzle answer was <code>8336623059567</code>.</p><p class="day-success">Both parts of this puzzle are complete! They provide two gold stars: **</p>
 145 <p>At this point, you should <a href="/2021">return to your Advent calendar</a> and try another puzzle.</p>
 146 <p>If you still want to see it, you can <a href="14/input" target="_blank">get your puzzle input</a>.</p>
 147 <p>You can also <span class="share">[Share<span class="share-content">on
 148   <a href="https://twitter.com/intent/tweet?text=I%27ve+completed+%22Extended+Polymerization%22+%2D+Day+14+%2D+Advent+of+Code+2021&amp;url=https%3A%2F%2Fadventofcode%2Ecom%2F2021%2Fday%2F14&amp;related=ericwastl&amp;hashtags=AdventOfCode" target="_blank">Twitter</a>
 149   <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+%22Extended+Polymerization%22+%2D+Day+14+%2D+Advent+of+Code+2021+%23AdventOfCode+https%3A%2F%2Fadventofcode%2Ecom%2F2021%2Fday%2F14'}else{return false;}" target="_blank">Mastodon</a
 150 ></span>]</span> this puzzle.</p>
 151 </main>
 152
 153 <!-- ga -->
 154 <script>
 155 (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
 156 (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
 157 m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
 158 })(window,document,'script','//www.google-analytics.com/analytics.js','ga');
 159 ga('create', 'UA-69522494-1', 'auto');
 160 ga('set', 'anonymizeIp', true);
 161 ga('send', 'pageview');
 162 </script>
 163 <!-- /ga -->
 164 </body>
 165 </html>