Reorder days into src

1 files changed, 207 insertions, 0 deletions

diff --git a/src/20/part2 b/src/20/part2
new file mode 100644
index 0000000..bef65a3
--- /dev/null
+++ b/src/20/part2
@@ -0,0 +1,207 @@
+--- Part Two ---
+
+Strangely, the exit isn't open when you reach it.  Then, you remember: the ancient Plutonians were
+famous for building recursive spaces.
+
+The marked connections in the maze aren't portals: they physically connect to a larger or smaller
+copy of the maze. Specifically, the labeled tiles around the inside edge actually connect to a
+smaller copy of the same maze, and the smaller copy's inner labeled tiles connect to yet a
+smaller copy, and so on.
+
+When you enter the maze, you are at the outermost level; when at the outermost level, only the outer
+labels AA and ZZ function (as the start and end, respectively); all other outer labeled tiles are
+effectively walls. At any other level, AA and ZZ count as walls, but the other outer labeled tiles
+bring you one level outward.
+
+Your goal is to find a path through the maze that brings you back to ZZ at the outermost level of
+the maze.
+
+In the first example above, the shortest path is now the loop around the right side. If the starting
+level is 0, then taking the previously-shortest path would pass through BC (to level 1), DE (to
+level 2), and FG (back to level 1). Because this is not the outermost level, ZZ is a wall, and the
+only option is to go back around to BC, which would only send you even deeper into the recursive
+maze.
+
+In the second example above, there is no path that brings you to ZZ at the outermost level.
+
+Here is a more interesting example:
+
+             Z L X W       C                 
+             Z P Q B       K                 
+  ###########.#.#.#.#######.###############  
+  #...#.......#.#.......#.#.......#.#.#...#  
+  ###.#.#.#.#.#.#.#.###.#.#.#######.#.#.###  
+  #.#...#.#.#...#.#.#...#...#...#.#.......#  
+  #.###.#######.###.###.#.###.###.#.#######  
+  #...#.......#.#...#...#.............#...#  
+  #.#########.#######.#.#######.#######.###  
+  #...#.#    F       R I       Z    #.#.#.#  
+  #.###.#    D       E C       H    #.#.#.#  
+  #.#...#                           #...#.#  
+  #.###.#                           #.###.#  
+  #.#....OA                       WB..#.#..ZH
+  #.###.#                           #.#.#.#  
+CJ......#                           #.....#  
+  #######                           #######  
+  #.#....CK                         #......IC
+  #.###.#                           #.###.#  
+  #.....#                           #...#.#  
+  ###.###                           #.#.#.#  
+XF....#.#                         RF..#.#.#  
+  #####.#                           #######  
+  #......CJ                       NM..#...#  
+  ###.#.#                           #.###.#  
+RE....#.#                           #......RF
+  ###.###        X   X       L      #.#.#.#  
+  #.....#        F   Q       P      #.#.#.#  
+  ###.###########.###.#######.#########.###  
+  #.....#...#.....#.......#...#.....#.#...#  
+  #####.#.###.#######.#######.###.###.#.#.#  
+  #.......#.......#.#.#.#.#...#...#...#.#.#  
+  #####.###.#####.#.#.#.#.###.###.#.###.###  
+  #.......#.....#.#...#...............#...#  
+  #############.#.#.###.###################  
+               A O F   N                     
+               A A D   M                     
+
+One shortest path through the maze is the following:
+
+
+ - Walk from AA to XF (16 steps)
+
+ - Recurse into level 1 through XF (1 step)
+
+ - Walk from XF to CK (10 steps)
+
+ - Recurse into level 2 through CK (1 step)
+
+ - Walk from CK to ZH (14 steps)
+
+ - Recurse into level 3 through ZH (1 step)
+
+ - Walk from ZH to WB (10 steps)
+
+ - Recurse into level 4 through WB (1 step)
+
+ - Walk from WB to IC (10 steps)
+
+ - Recurse into level 5 through IC (1 step)
+
+ - Walk from IC to RF (10 steps)
+
+ - Recurse into level 6 through RF (1 step)
+
+ - Walk from RF to NM (8 steps)
+
+ - Recurse into level 7 through NM (1 step)
+
+ - Walk from NM to LP (12 steps)
+
+ - Recurse into level 8 through LP (1 step)
+
+ - Walk from LP to FD (24 steps)
+
+ - Recurse into level 9 through FD (1 step)
+
+ - Walk from FD to XQ (8 steps)
+
+ - Recurse into level 10 through XQ (1 step)
+
+ - Walk from XQ to WB (4 steps)
+
+ - Return to level 9 through WB (1 step)
+
+ - Walk from WB to ZH (10 steps)
+
+ - Return to level 8 through ZH (1 step)
+
+ - Walk from ZH to CK (14 steps)
+
+ - Return to level 7 through CK (1 step)
+
+ - Walk from CK to XF (10 steps)
+
+ - Return to level 6 through XF (1 step)
+
+ - Walk from XF to OA (14 steps)
+
+ - Return to level 5 through OA (1 step)
+
+ - Walk from OA to CJ (8 steps)
+
+ - Return to level 4 through CJ (1 step)
+
+ - Walk from CJ to RE (8 steps)
+
+ - Return to level 3 through RE (1 step)
+
+ - Walk from RE to IC (4 steps)
+
+ - Recurse into level 4 through IC (1 step)
+
+ - Walk from IC to RF (10 steps)
+
+ - Recurse into level 5 through RF (1 step)
+
+ - Walk from RF to NM (8 steps)
+
+ - Recurse into level 6 through NM (1 step)
+
+ - Walk from NM to LP (12 steps)
+
+ - Recurse into level 7 through LP (1 step)
+
+ - Walk from LP to FD (24 steps)
+
+ - Recurse into level 8 through FD (1 step)
+
+ - Walk from FD to XQ (8 steps)
+
+ - Recurse into level 9 through XQ (1 step)
+
+ - Walk from XQ to WB (4 steps)
+
+ - Return to level 8 through WB (1 step)
+
+ - Walk from WB to ZH (10 steps)
+
+ - Return to level 7 through ZH (1 step)
+
+ - Walk from ZH to CK (14 steps)
+
+ - Return to level 6 through CK (1 step)
+
+ - Walk from CK to XF (10 steps)
+
+ - Return to level 5 through XF (1 step)
+
+ - Walk from XF to OA (14 steps)
+
+ - Return to level 4 through OA (1 step)
+
+ - Walk from OA to CJ (8 steps)
+
+ - Return to level 3 through CJ (1 step)
+
+ - Walk from CJ to RE (8 steps)
+
+ - Return to level 2 through RE (1 step)
+
+ - Walk from RE to XQ (14 steps)
+
+ - Return to level 1 through XQ (1 step)
+
+ - Walk from XQ to FD (8 steps)
+
+ - Return to level 0 through FD (1 step)
+
+ - Walk from FD to ZZ (18 steps)
+
+
+This path takes a total of 396 steps to move from AA at the outermost layer to ZZ at the outermost
+layer.
+
+In your maze, when accounting for recursion, how many steps does it take to get from the open tile
+marked AA to the open tile marked ZZ, both at the outermost layer?
+
+