2023 Day 10 Complete!
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[1]Advent of Code
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• [2][About]
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• [3][Events]
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• [4][Shop]
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• [5][Settings]
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• [6][Log Out]
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br0xen [7](AoC++) 20*
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//[8]2023
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• [9][Calendar]
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• [10][AoC++]
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• [11][Sponsors]
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• [12][Leaderboard]
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• [13][Stats]
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Our [14]sponsors help make Advent of Code possible:
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[15]Kotlin by JetBrains - Jingle bells, Kotlin pals, coding all the way!
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Solve puzzles, catch our daily livestreams for expert guidance, embrace
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the joy of Kotlin, and engage with a fantastic community. Happy holidays
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and happy coding!
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--- Day 10: Pipe Maze ---
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You use the hang glider to ride the hot air from Desert Island all the way
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up to the floating metal island. This island is surprisingly cold and
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there definitely aren't any thermals to glide on, so you leave your hang
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glider behind.
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You wander around for a while, but you don't find any people or animals.
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However, you do occasionally find signposts labeled "[16]Hot Springs"
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pointing in a seemingly consistent direction; maybe you can find someone
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at the hot springs and ask them where the desert-machine parts are made.
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The landscape here is alien; even the flowers and trees are made of metal.
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As you stop to admire some metal grass, you notice something metallic
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scurry away in your peripheral vision and jump into a big pipe! It didn't
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look like any animal you've ever seen; if you want a better look, you'll
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need to get ahead of it.
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Scanning the area, you discover that the entire field you're standing on
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is densely packed with pipes; it was hard to tell at first because they're
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the same metallic silver color as the "ground". You make a quick sketch of
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all of the surface pipes you can see (your puzzle input).
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The pipes are arranged in a two-dimensional grid of tiles:
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• | is a vertical pipe connecting north and south.
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• - is a horizontal pipe connecting east and west.
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• L is a 90-degree bend connecting north and east.
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• J is a 90-degree bend connecting north and west.
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• 7 is a 90-degree bend connecting south and west.
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• F is a 90-degree bend connecting south and east.
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• . is ground; there is no pipe in this tile.
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• S is the starting position of the animal; there is a pipe on this
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tile, but your sketch doesn't show what shape the pipe has.
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Based on the acoustics of the animal's scurrying, you're confident the
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pipe that contains the animal is one large, continuous loop.
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For example, here is a square loop of pipe:
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.....
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.F-7.
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.|.|.
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.L-J.
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.....
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If the animal had entered this loop in the northwest corner, the sketch
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would instead look like this:
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.....
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.S-7.
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.|.|.
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.L-J.
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.....
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In the above diagram, the S tile is still a 90-degree F bend: you can tell
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because of how the adjacent pipes connect to it.
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Unfortunately, there are also many pipes that aren't connected to the
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loop! This sketch shows the same loop as above:
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-L|F7
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7S-7|
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L|7||
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-L-J|
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L|-JF
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In the above diagram, you can still figure out which pipes form the main
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loop: they're the ones connected to S, pipes those pipes connect to, pipes
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those pipes connect to, and so on. Every pipe in the main loop connects to
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its two neighbors (including S, which will have exactly two pipes
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connecting to it, and which is assumed to connect back to those two
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pipes).
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Here is a sketch that contains a slightly more complex main loop:
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..F7.
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.FJ|.
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SJ.L7
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|F--J
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LJ...
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Here's the same example sketch with the extra, non-main-loop pipe tiles
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also shown:
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7-F7-
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.FJ|7
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SJLL7
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|F--J
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LJ.LJ
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If you want to get out ahead of the animal, you should find the tile in
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the loop that is farthest from the starting position. Because the animal
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is in the pipe, it doesn't make sense to measure this by direct distance.
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Instead, you need to find the tile that would take the longest number of
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steps along the loop to reach from the starting point - regardless of
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which way around the loop the animal went.
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In the first example with the square loop:
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.....
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.S-7.
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.|.|.
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.L-J.
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.....
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You can count the distance each tile in the loop is from the starting
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point like this:
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.....
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.012.
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.1.3.
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.234.
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.....
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In this example, the farthest point from the start is 4 steps away.
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Here's the more complex loop again:
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..F7.
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.FJ|.
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SJ.L7
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|F--J
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LJ...
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Here are the distances for each tile on that loop:
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..45.
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.236.
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01.78
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14567
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23...
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Find the single giant loop starting at S. How many steps along the loop
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does it take to get from the starting position to the point farthest from
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the starting position?
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Your puzzle answer was 6942.
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--- Part Two ---
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You quickly reach the farthest point of the loop, but the animal never
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emerges. Maybe its nest is within the area enclosed by the loop?
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To determine whether it's even worth taking the time to search for such a
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nest, you should calculate how many tiles are contained within the loop.
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For example:
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...........
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.S-------7.
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.|F-----7|.
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.||.....||.
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.||.....||.
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.|L-7.F-J|.
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.|..|.|..|.
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.L--J.L--J.
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...........
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The above loop encloses merely four tiles - the two pairs of . in the
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southwest and southeast (marked I below). The middle . tiles (marked O
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below) are not in the loop. Here is the same loop again with those regions
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marked:
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...........
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.S-------7.
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.|F-----7|.
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.||OOOOO||.
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.||OOOOO||.
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.|L-7OF-J|.
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.|II|O|II|.
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.L--JOL--J.
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.....O.....
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In fact, there doesn't even need to be a full tile path to the outside for
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tiles to count as outside the loop - squeezing between pipes is also
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allowed! Here, I is still within the loop and O is still outside the loop:
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..........
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.S------7.
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.|F----7|.
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.||OOOO||.
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.||OOOO||.
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.|L-7F-J|.
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.|II||II|.
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.L--JL--J.
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..........
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In both of the above examples, 4 tiles are enclosed by the loop.
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Here's a larger example:
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.F----7F7F7F7F-7....
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.|F--7||||||||FJ....
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.||.FJ||||||||L7....
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FJL7L7LJLJ||LJ.L-7..
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L--J.L7...LJS7F-7L7.
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....F-J..F7FJ|L7L7L7
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....L7.F7||L7|.L7L7|
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.....|FJLJ|FJ|F7|.LJ
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....FJL-7.||.||||...
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....L---J.LJ.LJLJ...
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The above sketch has many random bits of ground, some of which are in the
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loop (I) and some of which are outside it (O):
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OF----7F7F7F7F-7OOOO
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O|F--7||||||||FJOOOO
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O||OFJ||||||||L7OOOO
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FJL7L7LJLJ||LJIL-7OO
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L--JOL7IIILJS7F-7L7O
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OOOOF-JIIF7FJ|L7L7L7
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OOOOL7IF7||L7|IL7L7|
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OOOOO|FJLJ|FJ|F7|OLJ
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OOOOFJL-7O||O||||OOO
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OOOOL---JOLJOLJLJOOO
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In this larger example, 8 tiles are enclosed by the loop.
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Any tile that isn't part of the main loop can count as being enclosed by
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the loop. Here's another example with many bits of junk pipe lying around
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that aren't connected to the main loop at all:
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FF7FSF7F7F7F7F7F---7
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L|LJ||||||||||||F--J
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FL-7LJLJ||||||LJL-77
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F--JF--7||LJLJ7F7FJ-
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L---JF-JLJ.||-FJLJJ7
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|F|F-JF---7F7-L7L|7|
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|FFJF7L7F-JF7|JL---7
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7-L-JL7||F7|L7F-7F7|
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L.L7LFJ|||||FJL7||LJ
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L7JLJL-JLJLJL--JLJ.L
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Here are just the tiles that are enclosed by the loop marked with I:
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FF7FSF7F7F7F7F7F---7
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L|LJ||||||||||||F--J
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FL-7LJLJ||||||LJL-77
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F--JF--7||LJLJIF7FJ-
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L---JF-JLJIIIIFJLJJ7
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|F|F-JF---7IIIL7L|7|
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|FFJF7L7F-JF7IIL---7
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7-L-JL7||F7|L7F-7F7|
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L.L7LFJ|||||FJL7||LJ
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L7JLJL-JLJLJL--JLJ.L
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In this last example, 10 tiles are enclosed by the loop.
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Figure out whether you have time to search for the nest by calculating the
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area within the loop. How many tiles are enclosed by the loop?
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Your puzzle answer was 297.
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Both parts of this puzzle are complete! They provide two gold stars: **
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At this point, you should [17]return to your Advent calendar and try
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another puzzle.
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If you still want to see it, you can [18]get your puzzle input.
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You can also [Shareon [19]Twitter [20]Mastodon] this puzzle.
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References
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Visible links
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1. https://adventofcode.com/
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2. https://adventofcode.com/2023/about
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3. https://adventofcode.com/2023/events
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4. https://teespring.com/stores/advent-of-code
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5. https://adventofcode.com/2023/settings
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6. https://adventofcode.com/2023/auth/logout
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7. Advent of Code Supporter
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https://adventofcode.com/2023/support
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8. https://adventofcode.com/2023
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9. https://adventofcode.com/2023
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10. https://adventofcode.com/2023/support
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11. https://adventofcode.com/2023/sponsors
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12. https://adventofcode.com/2023/leaderboard
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13. https://adventofcode.com/2023/stats
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14. https://adventofcode.com/2023/sponsors
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15. https://kotlinlang.org/
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16. https://en.wikipedia.org/wiki/Hot_spring
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17. https://adventofcode.com/2023
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18. https://adventofcode.com/2023/day/10/input
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19. https://twitter.com/intent/tweet?text=I%27ve+completed+%22Pipe+Maze%22+%2D+Day+10+%2D+Advent+of+Code+2023&url=https%3A%2F%2Fadventofcode%2Ecom%2F2023%2Fday%2F10&related=ericwastl&hashtags=AdventOfCode
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20. javascript:void(0);
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