day13.html

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   5 <title>Day 13 - 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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  88 <body>
  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">26*</span></div></div><div><h1 class="title-event">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span class="title-event-wrap">λy.</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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 106 <main>
 107 <article class="day-desc"><h2>--- Day 13: A Maze of Twisty Little Cubicles ---</h2><p>You arrive at the first floor of this new building to discover a much less welcoming environment than the shiny atrium of the last one.  Instead, you are in a maze of <span title="You are in a twisty alike of little cubicles, all maze.">twisty little cubicles</span>, all alike.</p>
 108 <p>Every location in this area is addressed by a pair of non-negative integers (<code>x,y</code>). Each such coordinate is either a wall or an open space. You can't move diagonally. The cube maze starts at <code>0,0</code> and seems to extend infinitely toward <em>positive</em> <code>x</code> and <code>y</code>; negative values are <em>invalid</em>, as they represent a location outside the building. You are in a small waiting area at <code>1,1</code>.</p>
 109 <p>While it seems chaotic, a nearby morale-boosting poster explains, the layout is actually quite logical. You can determine whether a given <code>x,y</code> coordinate will be a wall or an open space using a simple system:</p>
 110 <ul>
 111 <li>Find <code>x*x + 3*x + 2*x*y + y + y*y</code>.</li>
 112 <li>Add the office designer's favorite number (your puzzle input).</li>
 113 <li>Find the <a href="https://en.wikipedia.org/wiki/Binary_number">binary representation</a> of that sum; count the <em>number</em> of <a href="https://en.wikipedia.org/wiki/Bit">bits</a> that are <code>1</code>.
 114 <ul>
 115 <li>If the number of bits that are <code>1</code> is <em>even</em>, it's an <em>open space</em>.</li>
 116 <li>If the number of bits that are <code>1</code> is <em>odd</em>, it's a <em>wall</em>.</li>
 117 </ul>
 118 </li>
 119 </ul>
 120 <p>For example, if the office designer's favorite number were <code>10</code>, drawing walls as <code>#</code> and open spaces as <code>.</code>, the corner of the building containing <code>0,0</code> would look like this:</p>
 121 <pre><code>  0123456789
 122 0 .#.####.##
 123 1 ..#..#...#
 124 2 #....##...
 125 3 ###.#.###.
 126 4 .##..#..#.
 127 5 ..##....#.
 128 6 #...##.###
 129 </code></pre>
 130 <p>Now, suppose you wanted to reach <code>7,4</code>. The shortest route you could take is marked as <code>O</code>:</p>
 131 <pre><code>  0123456789
 132 0 .#.####.##
 133 1 .O#..#...#
 134 2 #OOO.##...
 135 3 ###O#.###.
 136 4 .##OO#OO#.
 137 5 ..##OOO.#.
 138 6 #...##.###
 139 </code></pre>
 140 <p>Thus, reaching <code>7,4</code> would take a minimum of <code>11</code> steps (starting from your current location, <code>1,1</code>).</p>
 141 <p>What is the <em>fewest number of steps required</em> for you to reach <code>31,39</code>?</p>
 142 </article>
 143 <p>Your puzzle answer was <code>82</code>.</p><article class="day-desc"><h2>--- Part Two ---</h2><p><em>How many locations</em> (distinct <code>x,y</code> coordinates, including your starting location) can you reach in at most <code>50</code> steps?</p>
 144 </article>
 145 <p>Your puzzle answer was <code>138</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="/2016">return to your advent calendar</a> and try another puzzle.</p>
 147 <p>Your puzzle input was <code class="puzzle-input">1362</code>.</p>
 148 <p>You can also <span class="share">[Share<span class="share-content">on
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 152 ></span>]</span> this puzzle.</p>
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