Add 2024 Day 16

2024/day16_reindeer_maze/challenge.md

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+It's time again for the [Reindeer Olympics](/2015/day/14)! This year, the big event is the *Reindeer Maze*, where the Reindeer compete for the *lowest score*.
+
+You and The Historians arrive to search for the Chief right as the event is about to start. It wouldn't hurt to watch a little, right?
+
+The Reindeer start on the Start Tile (marked `S`) facing *East* and need to reach the End Tile (marked `E`). They can move forward one tile at a time (increasing their score by `1` point), but never into a wall (`#`). They can also rotate clockwise or counterclockwise 90 degrees at a time (increasing their score by `1000` points).
+
+To figure out the best place to sit, you start by grabbing a map (your puzzle input) from a nearby kiosk. For example:
+
+```
+###############
+#.......#....E#
+#.#.###.#.###.#
+#.....#.#...#.#
+#.###.#####.#.#
+#.#.#.......#.#
+#.#.#####.###.#
+#...........#.#
+###.#.#####.#.#
+#...#.....#.#.#
+#.#.#.###.#.#.#
+#.....#...#.#.#
+#.###.#.#.#.#.#
+#S..#.....#...#
+###############
+
+```
+
+There are many paths through this maze, but taking any of the best paths would incur a score of only `*7036*`. This can be achieved by taking a total of `36` steps forward and turning 90 degrees a total of `7` times:
+
+```
+
+###############
+#.......#....E#
+#.#.###.#.###^#
+#.....#.#...#^#
+#.###.#####.#^#
+#.#.#.......#^#
+#.#.#####.###^#
+#..>>>>>>>>v#^#
+###^#.#####v#^#
+#>>^#.....#v#^#
+#^#.#.###.#v#^#
+#^....#...#v#^#
+#^###.#.#.#v#^#
+#S..#.....#>>^#
+###############
+
+```
+
+Here's a second example:
+
+```
+#################
+#...#...#...#..E#
+#.#.#.#.#.#.#.#.#
+#.#.#.#...#...#.#
+#.#.#.#.###.#.#.#
+#...#.#.#.....#.#
+#.#.#.#.#.#####.#
+#.#...#.#.#.....#
+#.#.#####.#.###.#
+#.#.#.......#...#
+#.#.###.#####.###
+#.#.#...#.....#.#
+#.#.#.#####.###.#
+#.#.#.........#.#
+#.#.#.#########.#
+#S#.............#
+#################
+
+```
+
+In this maze, the best paths cost `*11048*` points; following one such path would look like this:
+
+```
+#################
+#...#...#...#..E#
+#.#.#.#.#.#.#.#^#
+#.#.#.#...#...#^#
+#.#.#.#.###.#.#^#
+#>>v#.#.#.....#^#
+#^#v#.#.#.#####^#
+#^#v..#.#.#>>>>^#
+#^#v#####.#^###.#
+#^#v#..>>>>^#...#
+#^#v###^#####.###
+#^#v#>>^#.....#.#
+#^#v#^#####.###.#
+#^#v#^........#.#
+#^#v#^#########.#
+#S#>>^..........#
+#################
+
+```
+
+Note that the path shown above includes one 90 degree turn as the very first move, rotating the Reindeer from facing East to facing North.
+
+Analyze your map carefully. *What is the lowest score a Reindeer could possibly get?*
+
+Your puzzle answer was `101492`.
+
+\--- Part Two ---
+----------
+
+Now that you know what the best paths look like, you can figure out the best spot to sit.
+
+Every non-wall tile (`S`, `.`, or `E`) is equipped with places to sit along the edges of the tile. While determining which of these tiles would be the best spot to sit depends on a whole bunch of factors (how comfortable the seats are, how far away the bathrooms are, whether there's a pillar blocking your view, etc.), the most important factor is *whether the tile is on one of the best paths through the maze*. If you sit somewhere else, you'd miss all the action!
+
+So, you'll need to determine which tiles are part of *any* best path through the maze, including the `S` and `E` tiles.
+
+In the first example, there are `*45*` tiles (marked `O`) that are part of at least one of the various best paths through the maze:
+
+```
+###############
+#.......#....O#
+#.#.###.#.###O#
+#.....#.#...#O#
+#.###.#####.#O#
+#.#.#.......#O#
+#.#.#####.###O#
+#..OOOOOOOOO#O#
+###O#O#####O#O#
+#OOO#O....#O#O#
+#O#O#O###.#O#O#
+#OOOOO#...#O#O#
+#O###.#.#.#O#O#
+#O..#.....#OOO#
+###############
+
+```
+
+In the second example, there are `*64*` tiles that are part of at least one of the best paths:
+
+```
+#################
+#...#...#...#..O#
+#.#.#.#.#.#.#.#O#
+#.#.#.#...#...#O#
+#.#.#.#.###.#.#O#
+#OOO#.#.#.....#O#
+#O#O#.#.#.#####O#
+#O#O..#.#.#OOOOO#
+#O#O#####.#O###O#
+#O#O#..OOOOO#OOO#
+#O#O###O#####O###
+#O#O#OOO#..OOO#.#
+#O#O#O#####O###.#
+#O#O#OOOOOOO..#.#
+#O#O#O#########.#
+#O#OOO..........#
+#################
+
+```
+
+Analyze your map further. *How many tiles are part of at least one of the best paths through the maze?*
+
+Your puzzle answer was `543`.
+
+Both parts of this puzzle are complete! They provide two gold stars: \*\*
+
+At this point, you should [return to your Advent calendar](/2024) and try another puzzle.
+
+If you still want to see it, you can [get your puzzle input](16/input).