advent-of-code-23.html

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   5 <title>Day 23 - Advent of Code</title>
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  15 Oh, hello!  Funny seeing you here.
  16
  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.  You do risk spoiling a few
  19 surprises for yourself, though.  Best to play the normal way and discover
  20 everything as it was intended, I think.  The best surprises don't even appear
  21 in the source until you unlock them for real.
  22
  23 Please be careful with automated requests; I'm not Google, and I can only take
  24 so much traffic.  Please be considerate so that everyone gets to play.
  25
  26 If you're curious about how Advent of Code works, it's running on some custom
  27 Perl code. Other than a few integrations (auth, analytics, ads, social media),
  28 I built the whole thing myself, including the design, animations, prose, and
  29 all of the puzzles.
  30
  31 The puzzles probably took the longest; the easiest ones were around 45 minutes
  32 each, but the harder ones took 2-3 hours, some even longer than that. A lot of
  33 effort went into building this thing - I hope you're enjoying playing it as
  34 much as I enjoyed making it for you!
  35
  36 If you'd like to hang out, I'm @ericwastl on Twitter.
  37
  38 - Eric Wastl
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  89 -->
  90 <body>
  91 <header><h1><a href="/">Advent of Code</a></h1><div class="user">Neil Smith <span class="star-count">46*</span></div><nav><ul><li><a href="/about">[About]</a></li><li><a href="/stats">[Stats]</a></li><li><a href="/leaderboard">[Leaderboard]</a></li><li><a href="/settings">[Settings]</a></li><li><a href="/auth/logout">[Log out]</a></li></ul></nav></header>
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 105 <main>
 106 <article class="day-desc"><h2>--- Day 23: Opening the Turing Lock ---</h2><p>Little Jane Marie just got her very first computer for Christmas from some <span title="Definitely not Wintermute.">unknown benefactor</span>.  It comes with instructions and an example program, but the computer itself seems to be malfunctioning.  She's curious what the program does, and would like you to help her run it.</p>
 107 <p>The manual explains that the computer supports two <a href="https://en.wikipedia.org/wiki/Processor_register">registers</a> and six <a href="https://en.wikipedia.org/wiki/Instruction_set">instructions</a> (truly, it goes on to remind the reader, a state-of-the-art technology). The registers are named <code>a</code> and <code>b</code>, can hold any <a href="https://en.wikipedia.org/wiki/Natural_number">non-negative integer</a>, and begin with a value of <code>0</code>.  The instructions are as follows:</p>
 108 <ul>
 109 <li><code>hlf r</code> sets register <code>r</code> to <em>half</em> its current value, then continues with the next instruction.</li>
 110 <li><code>tpl r</code> sets register <code>r</code> to <em>triple</em> its current value, then continues with the next instruction.</li>
 111 <li><code>inc r</code> <em>increments</em> register <code>r</code>, adding <code>1</code> to it, then continues with the next instruction.</li>
 112 <li><code>jmp offset</code> is a <em>jump</em>; it continues with the instruction <code>offset</code> away <em>relative to itself</em>.</li>
 113 <li><code>jie r, offset</code> is like <code>jmp</code>, but only jumps if register <code>r</code> is <em>even</em> ("jump if even").</li>
 114 <li><code>jio r, offset</code> is like <code>jmp</code>, but only jumps if register <code>r</code> is <code>1</code> ("jump if <em>one</em>", not odd).</li>
 115 </ul>
 116 <p>All three jump instructions work with an <em>offset</em> relative to that instruction.  The offset is always written with a prefix <code>+</code> or <code>-</code> to indicate the direction of the jump (forward or backward, respectively).  For example, <code>jmp +1</code> would simply continue with the next instruction, while <code>jmp +0</code> would continuously jump back to itself forever.</p>
 117 <p>The program exits when it tries to run an instruction beyond the ones defined.</p>
 118 <p>For example, this program sets <code>a</code> to <code>2</code>, because the <code>jio</code> instruction causes it to skip the <code>tpl</code> instruction:</p>
 119 <pre><code>inc a
 120 jio a, +2
 121 tpl a
 122 inc a
 123 </code></pre>
 124 <p>What is <em>the value in register <code>b</code></em> when the program in your puzzle input is finished executing?</p>
 125 </article>
 126 <p>Your puzzle answer was <code>307</code>.</p><article class="day-desc"><h2>--- Part Two ---</h2><p>The unknown benefactor is <em>very</em> thankful for releasi-- er, helping little Jane Marie with her computer.  Definitely not to distract you, what is the value in register <code>b</code> after the program is finished executing if register <code>a</code> starts as <code>1</code> instead?</p>
 127 </article>
 128 <p>Your puzzle answer was <code>160</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="/">return to your advent calendar</a> and try another puzzle.</p>
 130 <p>If you still want to see it, you can <a href="/day/23/input" target="_blank">get your puzzle input</a>.</p>
 131 <p>You can also <span class="share">[Share<span class="share-content">on
 132   <a href="https://twitter.com/intent/tweet?text=I%27ve+completed+%22Opening+the+Turing+Lock%22+%2D+Day+23+%2D+Advent+of+Code&amp;url=http%3A%2F%2Fadventofcode%2Ecom%2Fday%2F23&amp;related=ericwastl&amp;hashtags=AdventOfCode" target="_blank">Twitter</a>
 133   <a href="https://plus.google.com/share?url=http%3A%2F%2Fadventofcode%2Ecom%2Fday%2F23" target="_blank">Google+</a>
 134   <a href="http://www.reddit.com/submit?url=http%3A%2F%2Fadventofcode%2Ecom%2Fday%2F23&amp;title=I%27ve+completed+%22Opening+the+Turing+Lock%22+%2D+Day+23+%2D+Advent+of+Code" target="_blank">Reddit</a
 135 ></span>]</span>
 136  this puzzle.</p>
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