problems/day06.html

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   5 <title>Day 6 - 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.
  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!
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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">12*</span></div></div><div><h1 class="title-event">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span class="title-event-wrap">/*</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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  93 <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://jobs.americanexpress.com/technology" target="_blank" onclick="if(ga)ga('send','event','sponsor','sidebar',this.href);" rel="noopener">American Express</a> - We architect, code and ship software that makes us an essential part of our customers’ digital lives. Work with the latest tech and back the engineering community through open source. Find your place in tech on #TeamAmex.</div></div>
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  98 <article class="day-desc"><h2>--- Day 6: Custom Customs ---</h2><p>As your flight approaches the regional airport where you'll switch to a much larger plane, <a href="https://en.wikipedia.org/wiki/Customs_declaration" target="_blank">customs declaration forms</a> are distributed to the passengers.</p>
  99 <p>The form asks a series of 26 yes-or-no questions marked <code>a</code> through <code>z</code>. All you need to do is identify the questions for which <em>anyone in your group</em> answers "yes". Since your group is just you, this doesn't take very long.</p>
 100 <p>However, the person sitting next to you seems to be experiencing a language barrier and asks if you can help. For each of the people in their group, you write down the questions for which they answer "yes", one per line.  For example:</p>
 101 <pre><code>abcx
 102 abcy
 103 abcz
 104 </code></pre>
 105 <p>In this group, there are <em><code>6</code></em> questions to which anyone answered "yes": <code>a</code>, <code>b</code>, <code>c</code>, <code>x</code>, <code>y</code>, and <code>z</code>. (Duplicate answers to the same question don't count extra; each question counts at most once.)</p>
 106 <p>Another group asks for your help, then another, and eventually you've collected answers from every group on the plane (your puzzle input). Each group's answers are separated by a blank line, and within each group, each person's answers are on a single line. For example:</p>
 107 <pre><code>abc
 108
 109 a
 110 b
 111 c
 112
 113 ab
 114 ac
 115
 116 a
 117 a
 118 a
 119 a
 120
 121 b
 122 </code></pre>
 123 <p>This list represents answers from five groups:</p>
 124 <ul>
 125 <li>The first group contains one person who answered "yes" to <em><code>3</code></em> questions: <code>a</code>, <code>b</code>, and <code>c</code>.</li>
 126 <li>The second group contains three people; combined, they answered "yes" to <em><code>3</code></em> questions: <code>a</code>, <code>b</code>, and <code>c</code>.</li>
 127 <li>The third group contains two people; combined, they answered "yes" to <em><code>3</code></em> questions: <code>a</code>, <code>b</code>, and <code>c</code>.</li>
 128 <li>The fourth group contains four people; combined, they answered "yes" to only <em><code>1</code></em> question, <code>a</code>.</li>
 129 <li>The last group contains one person who answered "yes" to only <em><code>1</code></em> question, <code>b</code>.</li>
 130 </ul>
 131 <p>In this example, the sum of these counts is <code>3 + 3 + 3 + 1 + 1</code> = <em><code>11</code></em>.</p>
 132 <p>For each group, count the number of questions to which anyone answered "yes". <em>What is the sum of those counts?</em></p>
 133 </article>
 134 <p>Your puzzle answer was <code>6683</code>.</p><article class="day-desc"><h2 id="part2">--- Part Two ---</h2><p>As you finish the last group's customs declaration, you notice that <span title="Don't worry, nobody ever misreads just one word in real life.">you misread one word</span> in the instructions:</p>
 135 <p>You don't need to identify the questions to which <em>anyone</em> answered "yes"; you need to identify the questions to which <em>everyone</em> answered "yes"!</p>
 136 <p>Using the same  example as above:</p>
 137 <pre><code>abc
 138
 139 a
 140 b
 141 c
 142
 143 ab
 144 ac
 145
 146 a
 147 a
 148 a
 149 a
 150
 151 b
 152 </code></pre>
 153 <p>This list represents answers from five groups:</p>
 154 <ul>
 155 <li>In the first group, everyone (all 1 person) answered "yes" to <em><code>3</code></em> questions: <code>a</code>, <code>b</code>, and <code>c</code>.</li>
 156 <li>In the second group, there is <em>no</em> question to which everyone answered "yes".</li>
 157 <li>In the third group, everyone answered yes to only <em><code>1</code></em> question, <code>a</code>. Since some people did not answer "yes" to <code>b</code> or <code>c</code>, they don't count.</li>
 158 <li>In the fourth group, everyone answered yes to only <em><code>1</code></em> question, <code>a</code>.</li>
 159 <li>In the fifth group, everyone (all 1 person) answered "yes" to <em><code>1</code></em> question, <code>b</code>.</li>
 160 </ul>
 161 <p>In this example, the sum of these counts is <code>3 + 0 + 1 + 1 + 1</code> = <em><code>6</code></em>.</p>
 162 <p>For each group, count the number of questions to which <em>everyone</em> answered "yes". <em>What is the sum of those counts?</em></p>
 163 </article>
 164 <p>Your puzzle answer was <code>3122</code>.</p><p class="day-success">Both parts of this puzzle are complete! They provide two gold stars: **</p>
 165 <p>At this point, you should <a href="/2020">return to your Advent calendar</a> and try another puzzle.</p>
 166 <p>If you still want to see it, you can <a href="6/input" target="_blank">get your puzzle input</a>.</p>
 167 <p>You can also <span class="share">[Share<span class="share-content">on
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