aoc-2018-python

Advent of Code 2018 Solutions in Python
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part2 (6035B)


      1--- Part Two ---
      2
      3Strangely, the exit isn't open when you reach it.  Then, you remember: the ancient Plutonians were
      4famous for building recursive spaces.
      5
      6The marked connections in the maze aren't portals: they physically connect to a larger or smaller
      7copy of the maze. Specifically, the labeled tiles around the inside edge actually connect to a
      8smaller copy of the same maze, and the smaller copy's inner labeled tiles connect to yet a
      9smaller copy, and so on.
     10
     11When you enter the maze, you are at the outermost level; when at the outermost level, only the outer
     12labels AA and ZZ function (as the start and end, respectively); all other outer labeled tiles are
     13effectively walls. At any other level, AA and ZZ count as walls, but the other outer labeled tiles
     14bring you one level outward.
     15
     16Your goal is to find a path through the maze that brings you back to ZZ at the outermost level of
     17the maze.
     18
     19In the first example above, the shortest path is now the loop around the right side. If the starting
     20level is 0, then taking the previously-shortest path would pass through BC (to level 1), DE (to
     21level 2), and FG (back to level 1). Because this is not the outermost level, ZZ is a wall, and the
     22only option is to go back around to BC, which would only send you even deeper into the recursive
     23maze.
     24
     25In the second example above, there is no path that brings you to ZZ at the outermost level.
     26
     27Here is a more interesting example:
     28
     29             Z L X W       C                 
     30             Z P Q B       K                 
     31  ###########.#.#.#.#######.###############  
     32  #...#.......#.#.......#.#.......#.#.#...#  
     33  ###.#.#.#.#.#.#.#.###.#.#.#######.#.#.###  
     34  #.#...#.#.#...#.#.#...#...#...#.#.......#  
     35  #.###.#######.###.###.#.###.###.#.#######  
     36  #...#.......#.#...#...#.............#...#  
     37  #.#########.#######.#.#######.#######.###  
     38  #...#.#    F       R I       Z    #.#.#.#  
     39  #.###.#    D       E C       H    #.#.#.#  
     40  #.#...#                           #...#.#  
     41  #.###.#                           #.###.#  
     42  #.#....OA                       WB..#.#..ZH
     43  #.###.#                           #.#.#.#  
     44CJ......#                           #.....#  
     45  #######                           #######  
     46  #.#....CK                         #......IC
     47  #.###.#                           #.###.#  
     48  #.....#                           #...#.#  
     49  ###.###                           #.#.#.#  
     50XF....#.#                         RF..#.#.#  
     51  #####.#                           #######  
     52  #......CJ                       NM..#...#  
     53  ###.#.#                           #.###.#  
     54RE....#.#                           #......RF
     55  ###.###        X   X       L      #.#.#.#  
     56  #.....#        F   Q       P      #.#.#.#  
     57  ###.###########.###.#######.#########.###  
     58  #.....#...#.....#.......#...#.....#.#...#  
     59  #####.#.###.#######.#######.###.###.#.#.#  
     60  #.......#.......#.#.#.#.#...#...#...#.#.#  
     61  #####.###.#####.#.#.#.#.###.###.#.###.###  
     62  #.......#.....#.#...#...............#...#  
     63  #############.#.#.###.###################  
     64               A O F   N                     
     65               A A D   M                     
     66
     67One shortest path through the maze is the following:
     68
     69
     70 - Walk from AA to XF (16 steps)
     71
     72 - Recurse into level 1 through XF (1 step)
     73
     74 - Walk from XF to CK (10 steps)
     75
     76 - Recurse into level 2 through CK (1 step)
     77
     78 - Walk from CK to ZH (14 steps)
     79
     80 - Recurse into level 3 through ZH (1 step)
     81
     82 - Walk from ZH to WB (10 steps)
     83
     84 - Recurse into level 4 through WB (1 step)
     85
     86 - Walk from WB to IC (10 steps)
     87
     88 - Recurse into level 5 through IC (1 step)
     89
     90 - Walk from IC to RF (10 steps)
     91
     92 - Recurse into level 6 through RF (1 step)
     93
     94 - Walk from RF to NM (8 steps)
     95
     96 - Recurse into level 7 through NM (1 step)
     97
     98 - Walk from NM to LP (12 steps)
     99
    100 - Recurse into level 8 through LP (1 step)
    101
    102 - Walk from LP to FD (24 steps)
    103
    104 - Recurse into level 9 through FD (1 step)
    105
    106 - Walk from FD to XQ (8 steps)
    107
    108 - Recurse into level 10 through XQ (1 step)
    109
    110 - Walk from XQ to WB (4 steps)
    111
    112 - Return to level 9 through WB (1 step)
    113
    114 - Walk from WB to ZH (10 steps)
    115
    116 - Return to level 8 through ZH (1 step)
    117
    118 - Walk from ZH to CK (14 steps)
    119
    120 - Return to level 7 through CK (1 step)
    121
    122 - Walk from CK to XF (10 steps)
    123
    124 - Return to level 6 through XF (1 step)
    125
    126 - Walk from XF to OA (14 steps)
    127
    128 - Return to level 5 through OA (1 step)
    129
    130 - Walk from OA to CJ (8 steps)
    131
    132 - Return to level 4 through CJ (1 step)
    133
    134 - Walk from CJ to RE (8 steps)
    135
    136 - Return to level 3 through RE (1 step)
    137
    138 - Walk from RE to IC (4 steps)
    139
    140 - Recurse into level 4 through IC (1 step)
    141
    142 - Walk from IC to RF (10 steps)
    143
    144 - Recurse into level 5 through RF (1 step)
    145
    146 - Walk from RF to NM (8 steps)
    147
    148 - Recurse into level 6 through NM (1 step)
    149
    150 - Walk from NM to LP (12 steps)
    151
    152 - Recurse into level 7 through LP (1 step)
    153
    154 - Walk from LP to FD (24 steps)
    155
    156 - Recurse into level 8 through FD (1 step)
    157
    158 - Walk from FD to XQ (8 steps)
    159
    160 - Recurse into level 9 through XQ (1 step)
    161
    162 - Walk from XQ to WB (4 steps)
    163
    164 - Return to level 8 through WB (1 step)
    165
    166 - Walk from WB to ZH (10 steps)
    167
    168 - Return to level 7 through ZH (1 step)
    169
    170 - Walk from ZH to CK (14 steps)
    171
    172 - Return to level 6 through CK (1 step)
    173
    174 - Walk from CK to XF (10 steps)
    175
    176 - Return to level 5 through XF (1 step)
    177
    178 - Walk from XF to OA (14 steps)
    179
    180 - Return to level 4 through OA (1 step)
    181
    182 - Walk from OA to CJ (8 steps)
    183
    184 - Return to level 3 through CJ (1 step)
    185
    186 - Walk from CJ to RE (8 steps)
    187
    188 - Return to level 2 through RE (1 step)
    189
    190 - Walk from RE to XQ (14 steps)
    191
    192 - Return to level 1 through XQ (1 step)
    193
    194 - Walk from XQ to FD (8 steps)
    195
    196 - Return to level 0 through FD (1 step)
    197
    198 - Walk from FD to ZZ (18 steps)
    199
    200
    201This path takes a total of 396 steps to move from AA at the outermost layer to ZZ at the outermost
    202layer.
    203
    204In your maze, when accounting for recursion, how many steps does it take to get from the open tile
    205marked AA to the open tile marked ZZ, both at the outermost layer?
    206
    207