problems/day08.html

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   5 <title>Day 8 - Advent of Code 2017</title>
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  16 Oh, hello!  Funny seeing you here.
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  18 I appreciate your enthusiasm, but you aren't going to find much down here.
  19 There certainly aren't clues to any of the puzzles.  The best surprises don't
  20 even appear in the source until you unlock them for real.
  21
  22 Please be careful with automated requests; I'm not Google, and I can only take
  23 so much traffic.  Please be considerate so that everyone gets to play.
  24
  25 If you're curious about how Advent of Code works, it's running on some custom
  26 Perl code. Other than a few integrations (auth, analytics, ads, social media),
  27 I built the whole thing myself, including the design, animations, prose, and
  28 all of the puzzles.
  29
  30 The puzzles probably took the longest; the easiest ones took an hour or two
  31 each, but the harder ones took 4-5 hours, and a few even longer than that. A
  32 lot of effort went into building this thing - I hope you're enjoying playing it
  33 as much as I enjoyed making it for you!
  34
  35 If you'd like to hang out, I'm @ericwastl on Twitter.
  36
  37 - Eric Wastl
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  89 <body>
  90 <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">18*</span></div></div><div><h1 class="title-event">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<span class="title-event-wrap">/*</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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 108 <article class="day-desc"><h2>--- Day 8: I Heard You Like Registers ---</h2><p>You receive a <span title="There's that sorcery I told you about.">signal</span> directly from the CPU. Because of your recent assistance with <a href="5">jump instructions</a>, it would like you to compute the result of a series of unusual register instructions.</p>
 109 <p>Each instruction consists of several parts: the register to modify, whether to increase or decrease that register's value, the amount by which to increase or decrease it, and a condition. If the condition fails, skip the instruction without modifying the register. The registers all start at <code>0</code>. The instructions look like this:</p>
 110 <pre><code>b inc 5 if a &gt; 1
 111 a inc 1 if b &lt; 5
 112 c dec -10 if a &gt;= 1
 113 c inc -20 if c == 10
 114 </code></pre>
 115 <p>These instructions would be processed as follows:</p>
 116 <ul>
 117 <li>Because <code>a</code> starts at <code>0</code>, it is not greater than <code>1</code>, and so <code>b</code> is not modified.</li>
 118 <li><code>a</code> is increased by <code>1</code> (to <code>1</code>) because <code>b</code> is less than <code>5</code> (it is <code>0</code>).</li>
 119 <li><code>c</code> is decreased by <code>-10</code> (to <code>10</code>) because <code>a</code> is now greater than or equal to <code>1</code> (it is <code>1</code>).</li>
 120 <li><code>c</code> is increased by <code>-20</code> (to <code>-10</code>) because <code>c</code> is equal to <code>10</code>.</li>
 121 </ul>
 122 <p>After this process, the largest value in any register is <code>1</code>.</p>
 123 <p>You might also encounter <code>&lt;=</code> (less than or equal to) or <code>!=</code> (not equal to). However, the CPU doesn't have the bandwidth to tell you what all the registers are named, and leaves that to you to determine.</p>
 124 <p><em>What is the largest value in any register</em> after completing the instructions in your puzzle input?</p>
 125 </article>
 126 <p>Your puzzle answer was <code>4647</code>.</p><article class="day-desc"><h2>--- Part Two ---</h2><p>To be safe, the CPU also needs to know <em>the highest value held in any register during this process</em> so that it can decide how much memory to allocate to these operations. For example, in the above instructions, the highest value ever held was <code>10</code> (in register <code>c</code> after the third instruction was evaluated).</p>
 127 </article>
 128 <p>Your puzzle answer was <code>5590</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="8/input" target="_blank">get your puzzle input</a>.</p>
 131 <p>You can also <span class="share">[Share<span class="share-content">on
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 135 ></span>]</span> this puzzle.</p>
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