2015adventofcode/4.htm at master · benblankley/2015adventofcode · GitHub

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<title>Day 4 - Advent of Code</title>
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Oh, hello!  Funny seeing you here.

I appreciate your enthusiasm, but you aren't going to find much down here.
There certainly aren't clues to any of the puzzles.  You do risk spoiling a few
surprises for yourself, though.  Best to play the normal way and discover
everything as it was intended, I think.  The best surprises don't even appear
in the source until you unlock them for real.

Please be careful with automated requests; I'm not Google, and I can only take
so much traffic.  Please be considerate so that everyone gets to play.

If you're curious about how Advent of Code works, it's running on some custom
Perl code. Other than a few integrations (auth, analytics, ads, social media),
I built the whole thing myself, including the design, animations, prose, and
all of the puzzles.

The puzzles probably took the longest; the easiest ones were around 45 minutes
each, but the harder ones took 2-3 hours, some even longer than that. A lot of
effort went into building this thing - I hope you're enjoying playing it as
much as I enjoyed making it for you!

If you'd like to hang out, I'm @ericwastl on Twitter.

- Eric Wastl


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<header><h1><a href="/">Advent of Code</a></h1><div class="user">Ben Blankley <span class="star-count">12*</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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<article class="day-desc"><h2>--- Day 4: The Ideal Stocking Stuffer ---</h2><p>Santa needs help <a href="https://en.wikipedia.org/wiki/Bitcoin#Mining">mining</a> some <span title="Hey, mined your own business!">AdventCoins</span> (very similar to <a href="https://en.wikipedia.org/wiki/Bitcoin">bitcoins</a>) to use as gifts for all the economically forward-thinking little girls and boys.</p>
<p>To do this, he needs to find <a href="https://en.wikipedia.org/wiki/MD5">MD5</a> hashes which, in <a href="https://en.wikipedia.org/wiki/Hexadecimal">hexadecimal</a>, start with at least <em>five zeroes</em>.  The input to the MD5 hash is some secret key (your puzzle input, given below) followed by a number in decimal. To mine AdventCoins, you must find Santa the lowest positive number (no leading zeroes: <code>1</code>, <code>2</code>, <code>3</code>, ...) that produces such a hash.</p>
<p>For example:</p>
<ul>
<li>If your secret key is <code>abcdef</code>, the answer is <code>609043</code>, because the MD5 hash of <code>abcdef609043</code> starts with five zeroes (<code>000001dbbfa...</code>), and it is the lowest such number to do so.</li>
<li>If your secret key is <code>pqrstuv</code>, the lowest number it combines with to make an MD5 hash starting with five zeroes is <code>1048970</code>; that is, the MD5 hash of <code>pqrstuv1048970</code> looks like <code>000006136ef...</code>.</li>
</ul>
</article>
<p>Your puzzle answer was <code>117946</code>.</p><article class="day-desc"><h2>--- Part Two ---</h2><p>Now find one that starts with <em>six zeroes</em>.</p>
</article>
<p>Your puzzle answer was <code>3938038</code>.</p><p class="day-success">Both parts of this puzzle are complete! They provide two gold stars: **</p>
<p>At this point, you should <a href="/">return to your advent calendar</a> and try another puzzle.</p>
<p>Your puzzle input was <code class="puzzle-input">ckczppom</code>.</p>
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 this puzzle.</p>
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