60 lines
2.7 KiB
Markdown
60 lines
2.7 KiB
Markdown
You haven't even left yet and the group of Elvish Senior Historians has already
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hit a problem: their list of locations to check is currently empty. Eventually,
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someone decides that the best place to check first would be the Chief
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Historian's office.
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Upon pouring into the office, everyone confirms that the Chief Historian is
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indeed nowhere to be found. Instead, the Elves discover an assortment of notes
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and lists of historically significant locations! This seems to be the planning
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the Chief Historian was doing before he left. Perhaps these notes can be used
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to determine which locations to search?
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Throughout the Chief's office, the historically significant locations are listed
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not by name but by a unique number called the location ID. To make sure they
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don't miss anything, The Historians split into two groups, each searching the
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office and trying to create their own complete list of location IDs.
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There's just one problem: by holding the two lists up side by side (your puzzle
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input), it quickly becomes clear that the lists aren't very similar. Maybe you
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can help The Historians reconcile their lists?
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For example:
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```
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3 4
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4 3
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2 5
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1 3
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3 9
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3 3
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```
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Maybe the lists are only off by a small
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amount! To find out, pair up the numbers and measure how far apart they are.
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Pair up the smallest number in the left list with the smallest number in the
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right list, then the second-smallest left number with the second-smallest right
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number, and so on.
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Within each pair, figure out how far apart the two numbers are; you'll need to
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add up all of those distances. For example, if you pair up a 3 from the left
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list with a 7 from the right list, the distance apart is 4; if you pair up a 9
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with a 3, the distance apart is 6.
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In the example list above, the pairs and distances would be as follows:
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The smallest number in the left list is 1, and the smallest number in the right
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list is 3. The distance between them is 2. The second-smallest number in the
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left list is 2, and the second-smallest number in the right list is another 3.
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The distance between them is 1. The third-smallest number in both lists is 3,
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so the distance between them is 0. The next numbers to pair up are 3 and 4, a
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distance of 1. The fifth-smallest numbers in each list are 3 and 5, a distance
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of 2. Finally, the largest number in the left list is 4, while the largest
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number in the right list is 9; these are a distance 5 apart. To find the total
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distance between the left list and the right list, add up the distances between
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all of the pairs you found. In the example above, this is 2 + 1 + 0 + 1 + 2 +
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5, a total distance of 11!
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Your actual left and right lists contain many location IDs. What is the total
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distance between your lists?
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