problems/day03.html

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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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  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;<span class="title-event-wrap">sub y{</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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 106 <main>
 107 <article class="day-desc"><h2>--- Day 3: Spiral Memory ---</h2><p>You come across an experimental new kind of memory stored on an <span title="Good thing we have all these infinite two-dimensional grids lying around!">infinite two-dimensional grid</span>.</p>
 108 <p>Each square on the grid is allocated in a spiral pattern starting at a location marked <code>1</code> and then counting up while spiraling outward. For example, the first few squares are allocated like this:</p>
 109 <pre><code>17  16  15  14  13
 110 18   5   4   3  12
 111 19   6   1   2  11
 112 20   7   8   9  10
 113 21  22  23---&gt; ...
 114 </code></pre>
 115 <p>While this is very space-efficient (no squares are skipped), requested data must be carried back to square <code>1</code> (the location of the only access port for this memory system) by programs that can only move up, down, left, or right. They always take the shortest path: the <a href="https://en.wikipedia.org/wiki/Taxicab_geometry">Manhattan Distance</a> between the location of the data and square <code>1</code>.</p>
 116 <p>For example:</p>
 117 <ul>
 118 <li>Data from square <code>1</code> is carried <code>0</code> steps, since it's at the access port.</li>
 119 <li>Data from square <code>12</code> is carried <code>3</code> steps, such as: down, left, left.</li>
 120 <li>Data from square <code>23</code> is carried only <code>2</code> steps: up twice.</li>
 121 <li>Data from square <code>1024</code> must be carried <code>31</code> steps.</li>
 122 </ul>
 123 <p><em>How many steps</em> are required to carry the data from the square identified in your puzzle input all the way to the access port?</p>
 124 </article>
 125 <p>Your puzzle answer was <code>480</code>.</p><article class="day-desc"><h2>--- Part Two ---</h2><p>As a stress test on the system, the programs here clear the grid and then store the value <code>1</code> in square <code>1</code>. Then, in the same allocation order as shown above, they store the sum of the values in all adjacent squares, including diagonals.</p>
 126 <p>So, the first few squares' values are chosen as follows:</p>
 127 <ul>
 128 <li>Square <code>1</code> starts with the value <code>1</code>.</li>
 129 <li>Square <code>2</code> has only one adjacent filled square (with value <code>1</code>), so it also stores <code>1</code>.</li>
 130 <li>Square <code>3</code> has both of the above squares as neighbors and stores the sum of their values, <code>2</code>.</li>
 131 <li>Square <code>4</code> has all three of the aforementioned squares as neighbors and stores the sum of their values, <code>4</code>.</li>
 132 <li>Square <code>5</code> only has the first and fourth squares as neighbors, so it gets the value <code>5</code>.</li>
 133 </ul>
 134 <p>Once a square is written, its value does not change. Therefore, the first few squares would receive the following values:</p>
 135 <pre><code>147  142  133  122   59
 136 304    5    4    2   57
 137 330   10    1    1   54
 138 351   11   23   25   26
 139 362  747  806---&gt;   ...
 140 </code></pre>
 141 <p>What is the <em>first value written</em> that is <em>larger</em> than your puzzle input?</p>
 142 </article>
 143 <p>Your puzzle answer was <code>349975</code>.</p><p class="day-success">Both parts of this puzzle are complete! They provide two gold stars: **</p>
 144 <p>At this point, you should <a href="/2017">return to your advent calendar</a> and try another puzzle.</p>
 145 <p>Your puzzle input was <code class="puzzle-input">347991</code>.</p>
 146 <p>You can also <span class="share">[Share<span class="share-content">on
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 150 ></span>]</span> this puzzle.</p>
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