154 lines
7.5 KiB
HTML
154 lines
7.5 KiB
HTML
<!DOCTYPE html>
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<html lang="en-us">
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<head>
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<meta charset="utf-8"/>
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<title>Day 4 - Advent of Code 2020</title>
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<link href='//fonts.googleapis.com/css?family=Source+Code+Pro:300&subset=latin,latin-ext' rel='stylesheet' type='text/css'/>
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</head><!--
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Oh, hello! Funny seeing you here.
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I appreciate your enthusiasm, but you aren't going to find much down here.
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There certainly aren't clues to any of the puzzles. The best surprises don't
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even appear in the source until you unlock them for real.
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Please be careful with automated requests; I'm not a massive company, and I can
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only take so much traffic. Please be considerate so that everyone gets to play.
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If you're curious about how Advent of Code works, it's running on some custom
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Perl code. Other than a few integrations (auth, analytics, ads, social media),
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I built the whole thing myself, including the design, animations, prose, and
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all of the puzzles.
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The puzzles are most of the work; preparing a new calendar and a new set of
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puzzles each year takes all of my free time for 4-5 months. A lot of effort
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went into building this thing - I hope you're enjoying playing it as much as I
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enjoyed making it for you!
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If you'd like to hang out, I'm @ericwastl on Twitter.
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- Eric Wastl
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-->
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<body>
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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/adventofcode-2019" 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">m42e <a href="/2020/support" class="supporter-badge" title="Advent of Code Supporter">(AoC++)</a> <span class="star-count">6*</span></div></div><div><h1 class="title-event"> <span class="title-event-wrap">y(</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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<div id="sidebar">
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<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://www.twilio.com/quest?utm_source=advent-of-code-20&utm_medium=website" target="_blank" onclick="if(ga)ga('send','event','sponsor','sidebar',this.href);" rel="noopener">TwilioQuest</a> - Learn to code and lead your intrepid crew on a mission to save The Cloud in TwilioQuest, a PC role-playing game inspired by classics of the 16-bit era. Free forever, and available now for Windows, Mac, and Linux.</div></div>
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</div><!--/sidebar-->
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<main>
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<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>
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<article class="day-desc"><h2>--- Day 4: Passport Processing ---</h2><p>You arrive at the airport only to realize that you grabbed your North Pole Credentials instead of your passport. While these documents are extremely similar, North Pole Credentials aren't issued by a country and therefore aren't actually valid documentation for travel in most of the world.</p>
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<p>It seems like you're not the only one having problems, though; a very long line has formed for the automatic passport scanners, and the delay could upset your travel itinerary.</p>
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<p>Due to some questionable network security, you realize you might be able to solve both of these problems at the same time.</p>
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<p>The automatic passport scanners are slow because they're having trouble <em>detecting which passports have all required fields</em>. The expected fields are as follows:</p>
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<ul>
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<li><code>byr</code> (Birth Year)</li>
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<li><code>iyr</code> (Issue Year)</li>
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<li><code>eyr</code> (Expiration Year)</li>
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<li><code>hgt</code> (Height)</li>
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<li><code>hcl</code> (Hair Color)</li>
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<li><code>ecl</code> (Eye Color)</li>
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<li><code>pid</code> (Passport ID)</li>
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<li><code>cid</code> (Country ID)</li>
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</ul>
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<p>Passport data is validated in batch files (your puzzle input). Each passport is represented as a sequence of <code>key:value</code> pairs separated by spaces or newlines. Passports are separated by blank lines.</p>
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<p>Here is an example batch file containing four passports:</p>
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<pre><code>ecl:gry pid:860033327 eyr:2020 hcl:#fffffd
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byr:1937 iyr:2017 cid:147 hgt:183cm
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iyr:2013 ecl:amb cid:350 eyr:2023 pid:028048884
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hcl:#cfa07d byr:1929
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hcl:#ae17e1 iyr:2013
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eyr:2024
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ecl:brn pid:760753108 byr:1931
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hgt:179cm
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hcl:#cfa07d eyr:2025 pid:166559648
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iyr:2011 ecl:brn hgt:59in
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</code></pre>
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<p>The first passport is <em>valid</em> - all eight fields are present. The second passport is <em>invalid</em> - it is missing <code>hgt</code> (the Height field).</p>
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<p>The third passport is interesting; the <em>only missing field</em> is <code>cid</code>, so it looks like data from North Pole Credentials, not a passport at all! Surely, nobody would mind if you made the system temporarily ignore missing <code>cid</code> fields. Treat this "passport" as <em>valid</em>.</p>
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<p>The fourth passport is missing two fields, <code>cid</code> and <code>byr</code>. Missing <code>cid</code> is fine, but missing any other field is not, so this passport is <em>invalid</em>.</p>
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<p>According to the above rules, your improved system would report <code><em>2</em></code> valid passports.</p>
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<p>Count the number of <em>valid</em> passports - those that have all required fields. Treat <code>cid</code> as optional. <em>In your batch file, how many passports are valid?</em></p>
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</article>
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<p>To begin, <a href="4/input" target="_blank">get your puzzle input</a>.</p>
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<form method="post" action="4/answer"><input type="hidden" name="level" value="1"/><p>Answer: <input type="text" name="answer" autocomplete="off"/> <input type="submit" value="[Submit]"/></p></form>
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<p>You can also <span class="share">[Share<span class="share-content">on
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<a href="https://twitter.com/intent/tweet?text=%22Passport+Processing%22+%2D+Day+4+%2D+Advent+of+Code+2020&url=https%3A%2F%2Fadventofcode%2Ecom%2F2020%2Fday%2F4&related=ericwastl&hashtags=AdventOfCode" target="_blank">Twitter</a>
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></span>]</span> this puzzle.</p>
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