advent-of-code-20.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.  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.
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  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!
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  36 If you'd like to hang out, I'm @ericwastl on Twitter.
  37
  38 - Eric Wastl
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  91 <header><h1><a href="/">Advent of Code</a></h1><div class="user">Neil Smith <span class="star-count">40*</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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 106 <article class="day-desc"><h2>--- Day 20: Infinite Elves and Infinite Houses ---</h2><p>To keep the Elves busy, Santa has them deliver some presents <span title="This was before the Elves unionized, apparently.">by hand, door-to-door</span>.  He sends them down a street with infinite houses numbered sequentially: <code>1</code>, <code>2</code>, <code>3</code>, <code>4</code>, <code>5</code>, and so on.</p>
 107 <p>Each Elf is assigned a number, too, and delivers presents to houses based on that number:</p>
 108 <ul>
 109 <li>The first Elf (number <code>1</code>) delivers presents to every house: <code>1</code>, <code>2</code>, <code>3</code>, <code>4</code>, <code>5</code>, ....</li>
 110 <li>The second Elf (number <code>2</code>) delivers presents to every second house: <code>2</code>, <code>4</code>, <code>6</code>, <code>8</code>, <code>10</code>, ....</li>
 111 <li>Elf number <code>3</code> delivers presents to every third house: <code>3</code>, <code>6</code>, <code>9</code>, <code>12</code>, <code>15</code>, ....</li>
 112 </ul>
 113 <p>There are infinitely many Elves, numbered starting with <code>1</code>.  Each Elf delivers presents equal to <em>ten times</em> his or her number at each house.</p>
 114 <p>So, the first nine houses on the street end up like this:</p>
 115 <pre><code>House 1 got 10 presents.
 116 House 2 got 30 presents.
 117 House 3 got 40 presents.
 118 House 4 got 70 presents.
 119 House 5 got 60 presents.
 120 House 6 got 120 presents.
 121 House 7 got 80 presents.
 122 House 8 got 150 presents.
 123 House 9 got 130 presents.
 124 </code></pre>
 125 <p>The first house gets <code>10</code> presents: it is visited only by Elf <code>1</code>, which delivers <code>1 * 10 = 10</code> presents.  The fourth house gets <code>70</code> presents, because it is visited by Elves <code>1</code>, <code>2</code>, and <code>4</code>, for a total of <code>10 + 20 + 40 = 70</code> presents.</p>
 126 <p>What is the <em>lowest house number</em> of the house to get at least as many presents as the number in your puzzle input?</p>
 127 </article>
 128 <p>Your puzzle answer was <code>776160</code>.</p><article class="day-desc"><h2>--- Part Two ---</h2><p>The Elves decide they don't want to visit an infinite number of houses.  Instead, each Elf will stop after delivering presents to <code>50</code> houses.  To make up for it, they decide to deliver presents equal to <em>eleven times</em> their number at each house.</p>
 129 <p>With these changes, what is the new <em>lowest house number</em> of the house to get at least as many presents as the number in your puzzle input?</p>
 130 </article>
 131 <p>Your puzzle answer was <code>786240</code>.</p><p class="day-success">Both parts of this puzzle are complete! They provide two gold stars: **</p>
 132 <p>At this point, you should <a href="/">return to your advent calendar</a> and try another puzzle.</p>
 133 <p>Your puzzle input was <code class="puzzle-input">33100000</code>.</p>
 134 <p>You can also <span class="share">[Share<span class="share-content">on
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 138 ></span>]</span>
 139  this puzzle.</p>
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