problems/day07.html

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   5 <title>Day 7 - Advent of Code 2020</title>
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  16 Oh, hello!  Funny seeing you here.
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  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.
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  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!
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  35 If you'd like to hang out, I'm @ericwastl on Twitter.
  36
  37 - Eric Wastl
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  90 <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">14*</span></div></div><div><h1 class="title-event">&nbsp;&nbsp;&nbsp;<span class="title-event-wrap">$year=</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>
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  98 <article class="day-desc"><h2>--- Day 7: Handy Haversacks ---</h2><p>You land at the regional airport in time for your next flight. In fact, it looks like you'll even have time to grab some food: all flights are currently delayed due to <em>issues in luggage processing</em>.</p>
  99 <p>Due to recent aviation regulations, many rules (your puzzle input) are being enforced about bags and their contents; bags must be color-coded and must contain specific quantities of other color-coded bags. Apparently, nobody responsible for these regulations considered how long they would take to enforce!</p>
 100 <p>For example, consider the following rules:</p>
 101 <pre><code>light red bags contain 1 bright white bag, 2 muted yellow bags.
 102 dark orange bags contain 3 bright white bags, 4 muted yellow bags.
 103 bright white bags contain 1 shiny gold bag.
 104 muted yellow bags contain 2 shiny gold bags, 9 faded blue bags.
 105 shiny gold bags contain 1 dark olive bag, 2 vibrant plum bags.
 106 dark olive bags contain 3 faded blue bags, 4 dotted black bags.
 107 vibrant plum bags contain 5 faded blue bags, 6 dotted black bags.
 108 faded blue bags contain no other bags.
 109 dotted black bags contain no other bags.
 110 </code></pre>
 111 <p>These rules specify the required contents for 9 bag types. In this example, every <code>faded blue</code> bag is empty, every <code>vibrant plum</code> bag contains 11 bags (5 <code>faded blue</code> and 6 <code>dotted black</code>), and so on.</p>
 112 <p>You have a <code><em>shiny gold</em></code> bag. If you wanted to carry it in at least one other bag, how many different bag colors would be valid for the outermost bag? (In other words: how many colors can, eventually, contain at least one <code>shiny gold</code> bag?)</p>
 113 <p>In the above rules, the following options would be available to you:</p>
 114 <ul>
 115 <li>A <code>bright white</code> bag, which can hold your <code>shiny gold</code> bag directly.</li>
 116 <li>A <code>muted yellow</code> bag, which can hold your <code>shiny gold</code> bag directly, plus some other bags.</li>
 117 <li>A <code>dark orange</code> bag, which can hold <code>bright white</code> and <code>muted yellow</code> bags, either of which could then hold your <code>shiny gold</code> bag.</li>
 118 <li>A <code>light red</code> bag, which can hold <code>bright white</code> and <code>muted yellow</code> bags, either of which could then hold your <code>shiny gold</code> bag.</li>
 119 </ul>
 120 <p>So, in this example, the number of bag colors that can eventually contain at least one <code>shiny gold</code> bag is <code><em>4</em></code>.</p>
 121 <p><em>How many bag colors can eventually contain at least one <code>shiny gold</code> bag?</em> (The list of rules is quite long; make sure you get all of it.)</p>
 122 </article>
 123 <p>Your puzzle answer was <code>242</code>.</p><article class="day-desc"><h2 id="part2">--- Part Two ---</h2><p>It's getting pretty expensive to fly these days - not because of ticket prices, but because of the ridiculous number of bags you need to buy!</p>
 124 <p>Consider again your <code>shiny gold</code> bag and the rules from the above example:</p>
 125 <ul>
 126 <li><code>faded blue</code> bags contain <code>0</code> other bags.</li>
 127 <li><code>dotted black</code> bags contain <code>0</code> other bags.</li>
 128 <li><code>vibrant plum</code> bags contain <code>11</code> other bags: 5 <code>faded blue</code> bags and 6 <code>dotted black</code> bags.</li>
 129 <li><code>dark olive</code> bags contain <code>7</code> other bags: 3 <code>faded blue</code> bags and 4 <code>dotted black</code> bags.</li>
 130 </ul>
 131 <p>So, a single <code>shiny gold</code> bag must contain 1 <code>dark olive</code> bag (and the 7 bags within it) plus 2 <code>vibrant plum</code> bags (and the 11 bags within <em>each</em> of those): <code>1 + 1*7 + 2 + 2*11</code> = <code><em>32</em></code> bags!</p>
 132 <p>Of course, the actual rules have a <span title="100%">small</span> chance of going several levels deeper than this example; be sure to count all of the bags, even if the nesting becomes topologically impractical!</p>
 133 <p>Here's another example:</p>
 134 <pre><code>shiny gold bags contain 2 dark red bags.
 135 dark red bags contain 2 dark orange bags.
 136 dark orange bags contain 2 dark yellow bags.
 137 dark yellow bags contain 2 dark green bags.
 138 dark green bags contain 2 dark blue bags.
 139 dark blue bags contain 2 dark violet bags.
 140 dark violet bags contain no other bags.
 141 </code></pre>
 142 <p>In this example, a single <code>shiny gold</code> bag must contain <code><em>126</em></code> other bags.</p>
 143 <p><em>How many individual bags are required inside your single <code>shiny gold</code> bag?</em></p>
 144 </article>
 145 <p>Your puzzle answer was <code>176035</code>.</p><p class="day-success">Both parts of this puzzle are complete! They provide two gold stars: **</p>
 146 <p>At this point, you should <a href="/2020">return to your Advent calendar</a> and try another puzzle.</p>
 147 <p>If you still want to see it, you can <a href="7/input" target="_blank">get your puzzle input</a>.</p>
 148 <p>You can also <span class="share">[Share<span class="share-content">on
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