day05.html

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   5 <title>Day 5 - Advent of Code 2016</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.
  20
  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.
  28
  29 The puzzles probably took the longest; the easiest ones were around 45 minutes
  30 each, but the harder ones took 2-3 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!
  33
  34 If you'd like to hang out, I'm @ericwastl on Twitter.
  35
  36 - Eric Wastl
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  89 <header><div><h1 class="title-global"><a href="/">Advent of Code</a></h1><nav><ul><li><a href="/2016/about">[About]</a></li><li><a href="/2016/support">[AoC++]</a></li><li><a href="/2016/events">[Events]</a></li><li><a href="/2016/settings">[Settings]</a></li><li><a href="/2016/auth/logout">[Log Out]</a></li></ul></nav><div class="user">Neil Smith <span class="supporter">(AoC++)</span> <span class="star-count">10*</span></div></div><div><h1 class="title-event">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span class="title-event-wrap">y(</span><a href="/2016">2016</a><span class="title-event-wrap">)</span></h1><nav><ul><li><a href="/2016">[Calendar]</a></li><li><a href="/2016/leaderboard">[Leaderboard]</a></li><li><a href="/2016/stats">[Stats]</a></li><li><a href="/2016/sponsors">[Sponsors]</a></li></ul></nav></div></header>
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 107 <article class="day-desc"><h2>--- Day 5: How About a Nice Game of Chess? ---</h2><p>You are faced with a security door designed by Easter Bunny engineers that seem to have acquired most of their security knowledge by watching <a href="https://en.wikipedia.org/wiki/Hackers_(film)">hacking</a> <a href="https://en.wikipedia.org/wiki/WarGames">movies</a>.</p>
 108 <p>The <em>eight-character password</em> for the door is generated one character at a time by finding the <a href="https://en.wikipedia.org/wiki/MD5">MD5</a> hash of some Door ID (your puzzle input) and an increasing integer index (starting with <code>0</code>).</p>
 109 <p>A hash indicates the <em>next character</em> in the password if its <a href="https://en.wikipedia.org/wiki/Hexadecimal">hexadecimal</a> representation starts with <em>five zeroes</em>. If it does, the sixth character in the hash is the next character of the password.</p>
 110 <p>For example, if the Door ID is <code>abc</code>:</p>
 111 <ul>
 112 <li>The first index which produces a hash that starts with five zeroes is <code>3231929</code>, which we find by hashing <code>abc3231929</code>; the sixth character of the hash, and thus the first character of the password, is <code>1</code>.</li>
 113 <li><code>5017308</code> produces the next interesting hash, which starts with <code>000008f82...</code>, so the second character of the password is <code>8</code>.</li>
 114 <li>The third time a hash starts with five zeroes is for <code>abc5278568</code>, discovering the character <code>f</code>.</li>
 115 </ul>
 116 <p>In this example, after continuing this search a total of eight times, the password is <code>18f47a30</code>.</p>
 117 <p>Given the actual Door ID, <em>what is the password</em>?</p>
 118 </article>
 119 <p>Your puzzle answer was <code>f77a0e6e</code>.</p><article class="day-desc"><h2>--- Part Two ---</h2><p>As the door slides open, you are presented with a second door that uses a slightly more <span title="This one says 'WOPR' in block letters.">inspired</span> security mechanism. Clearly unimpressed by the last version (in what movie is the password decrypted <em>in order</em>?!), the Easter Bunny engineers have worked out <a href="https://www.youtube.com/watch?v=NHWjlCaIrQo&t=25">a better solution</a>.</p>
 120 <p>Instead of simply filling in the password from left to right, the hash now also indicates the <em>position</em> within the password to fill. You still look for hashes that begin with five zeroes; however, now, the <em>sixth</em> character represents the <em>position</em> (<code>0</code>-<code>7</code>), and the <em>seventh</em> character is the character to put in that position.</p>
 121 <p>A hash result of <code>000001f</code> means that <code>f</code> is the <em>second</em> character in the password. Use only the <em>first result</em> for each position, and ignore invalid positions.</p>
 122 <p>For example, if the Door ID is <code>abc</code>:</p>
 123 <ul>
 124 <li>The first interesting hash is from <code>abc3231929</code>, which produces <code>0000015...</code>; so, <code>5</code> goes in position <code>1</code>: <code>_5______</code>.</li>
 125 <li>In the previous method, <code>5017308</code> produced an interesting hash; however, it is ignored, because it specifies an invalid position (<code>8</code>).</li>
 126 <li>The second interesting hash is at index <code>5357525</code>, which produces <code>000004e...</code>; so, <code>e</code> goes in position <code>4</code>: <code>_5__e___</code>.</li>
 127 </ul>
 128 <p>You almost choke on your popcorn as the final character falls into place, producing the password <code>05ace8e3</code>.</p>
 129 <p>Given the actual Door ID and this new method, <em>what is the password</em>? Be extra proud of your solution if it uses a cinematic "decrypting" animation.</p>
 130 </article>
 131 <p>Your puzzle answer was <code>999828ec</code>.</p><p class="day-success">Both parts of this puzzle are complete! They provide two gold stars: **</p>
 132 <p>At this point, you should <a href="/2016">return to your advent calendar</a> and try another puzzle.</p>
 133 <p>Your puzzle input was <code class="puzzle-input">cxdnnyjw</code>.</p>
 134 <p>You can also <span class="share">[Share<span class="share-content">on
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 138 ></span>]</span> this puzzle.</p>
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