problems/day04.html

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   5 <title>Day 4 - Advent of Code 2017</title>
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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.  The best surprises don't
  19 even appear in the source until you unlock them for real.
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  21 Please be careful with automated requests; I'm not Google, and I can only take
  22 so much traffic.  Please be considerate so that everyone gets to play.
  23
  24 If you're curious about how Advent of Code works, it's running on some custom
  25 Perl code. Other than a few integrations (auth, analytics, ads, social media),
  26 I built the whole thing myself, including the design, animations, prose, and
  27 all of the puzzles.
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  29 The puzzles probably took the longest; the easiest ones took an hour or two
  30 each, but the harder ones took 4-5 hours, and a few even longer than that. A
  31 lot of effort went into building this thing - I hope you're enjoying playing it
  32 as much as I enjoyed making it for you!
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  34 If you'd like to hang out, I'm @ericwastl on Twitter.
  35
  36 - Eric Wastl
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  87 -->
  88 <body>
  89 <header><div><h1 class="title-global"><a href="/">Advent of Code</a></h1><nav><ul><li><a href="/2017/about">[About]</a></li><li><a href="/2017/support">[AoC++]</a></li><li><a href="/2017/events">[Events]</a></li><li><a href="/2017/settings">[Settings]</a></li><li><a href="/2017/auth/logout">[Log Out]</a></li></ul></nav><div class="user">Neil Smith <span class="supporter">(AoC++)</span> <span class="star-count">12*</span></div></div><div><h1 class="title-event">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span class="title-event-wrap">λy.</span><a href="/2017">2017</a><span class="title-event-wrap"></span></h1><nav><ul><li><a href="/2017">[Calendar]</a></li><li><a href="/2017/leaderboard">[Leaderboard]</a></li><li><a href="/2017/stats">[Stats]</a></li><li><a href="/2017/sponsors">[Sponsors]</a></li></ul></nav></div></header>
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 107 <article class="day-desc"><h2>--- Day 4: High-Entropy Passphrases ---</h2><p>A new system policy has been put in place that requires all accounts to use a <em>passphrase</em> instead of simply a pass<em>word</em>. A passphrase consists of a series of words (lowercase letters) separated by spaces.</p>
 108 <p>To ensure security, a valid passphrase must contain no duplicate words.</p>
 109 <p>For example:</p>
 110 <ul>
 111 <li><code>aa bb cc dd ee</code> is valid.</li>
 112 <li><code>aa bb cc dd aa</code> is not valid - the word <code>aa</code> appears more than once.</li>
 113 <li><code>aa bb cc dd aaa</code> is valid - <code>aa</code> and <code>aaa</code> count as different words.</li>
 114 </ul>
 115 <p>The system's full passphrase list is available as your puzzle input. <em>How many passphrases are valid?</em></p>
 116 </article>
 117 <p>Your puzzle answer was <code>383</code>.</p><article class="day-desc"><h2>--- Part Two ---</h2><p>For added security, <span title="Because as everyone knows, the number of rules is proportional to the level of security.">yet another system policy</span> has been put in place.  Now, a valid passphrase must contain no two words that are anagrams of each other - that is, a passphrase is invalid if any word's letters can be rearranged to form any other word in the passphrase.</p>
 118 <p>For example:</p>
 119 <ul>
 120 <li><code>abcde fghij</code> is a valid passphrase.</li>
 121 <li><code>abcde xyz ecdab</code> is not valid - the letters from the third word can be rearranged to form the first word.</li>
 122 <li><code>a ab abc abd abf abj</code> is a valid passphrase, because <em>all</em> letters need to be used when forming another word.</li>
 123 <li><code>iiii oiii ooii oooi oooo</code> is valid.</li>
 124 <li><code>oiii ioii iioi iiio</code> is not valid - any of these words can be rearranged to form any other word.</li>
 125 </ul>
 126 <p>Under this new system policy, <em>how many passphrases are valid?</em></p>
 127 </article>
 128 <p>Your puzzle answer was <code>265</code>.</p><p class="day-success">Both parts of this puzzle are complete! They provide two gold stars: **</p>
 129 <p>At this point, you should <a href="/2017">return to your advent calendar</a> and try another puzzle.</p>
 130 <p>If you still want to see it, you can <a href="4/input" target="_blank">get your puzzle input</a>.</p>
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 135 ></span>]</span> this puzzle.</p>
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