commit 4dfcd34fb14a951d6c41d49a6cce650bbd988c27 · hauleth.dev/advent-of-code

+187

2024/day06.livemd

···

       1
       +
       <!-- livebook:{"persist_outputs":true} -->

     

       2
       +
       

     

       3
       +
       # Untitled notebook

     

       4
       +
       

     

       5
       +
       ```elixir

     

       6
       +
       Mix.install([:kino_aoc, :arrays])

     

       7
       +
       ```

     

       8
       +
       

     

       9
       +
       ## Section

     

       10
       +
       

     

       11
       +
       <!-- livebook:{"attrs":"eyJhc3NpZ25fdG8iOiJwdXp6bGVfaW5wdXQiLCJkYXkiOiI2Iiwic2Vzc2lvbl9zZWNyZXQiOiJBRFZFTlRfT0ZfQ09ERV9TRVNTSU9OIiwieWVhciI6IjIwMjQifQ","chunks":null,"kind":"Elixir.KinoAOC.HelperCell","livebook_object":"smart_cell"} -->

     

       12
       +
       

     

       13
       +
       ```elixir

     

       14
       +
       {:ok, puzzle_input} =

     

       15
       +
         KinoAOC.download_puzzle("2024", "6", System.fetch_env!("LB_ADVENT_OF_CODE_SESSION"))

     

       16
       +
       ```

     

       17
       +
       

     

       18
       +
       <!-- livebook:{"output":true} -->

     

       19
       +
       

     

       20
       +
       ```

     

       21
       +
       {:ok,

     

       22
       +
        "...#..................#...................#......................#..............................#.............................#...\n....#.......................#........#.#..............##...........#.....#..........#..........................#..................\n.............#........................................................................#.........#.#..#..#..........#..............\n..........#.......#..........#..................#........##...................#..............#....................................\n....................#..........................................................#..#.....................................#.........\n....#............................#..............................................#.....................#..........##....#..........\n.......#.............#......................................................................#.............#.........#.............\n....###......................#....#...........#.....#................................#..........................#.................\n..........#..#...........#..#........................................................#.....#...........#................#.........\n..#....#......#....#....#...................................................................#.....................................\n....................#............#............................................#......#....#...............................#.......\n..........#.......#.........#.......#.............................................................................................\n.......#...#.......................................#...................#..........................................................\n.......#........#............................#.....#.......#..............................................#..................#...#\n.....................#.................................#................#...#...............#.....#.#..........................#..\n.....#..........................................#......................#.............##..............................#........#...\n.....#......#.........................#..........................#..........................................................#..#..\n.#......#.............#......#.................................................#.....#...................##......#................\n.............................................................................##...................................................\n........................................#.......................................#........#.............................#.#.......#\n...........#.....................................#.............................#......#......#..#....................#..#.........\n.............................................#.......................#..................##....#.....#.............................\n........................#..............................................................#..........................................\n#..............#.........................#........#...#...............#..............#..................#....................##...\n...#...#.............................#.......#................................................#........................#....#.....\n.....#.........................#..#.......................#..........#.....................#..................#.#.....#...........\n..................#........#..#.......#...................................................................................#....#..\n..#...#...............................................#.#..#........................................................#....#......#.\n...............#...............#..........................#............................#..........#.............#.................\n............#.....#........#.........................................................#........#........#.....#........#......#....\n............................#.........#....#........#.....#...#.............#.................................#...................\n........#..................#....#.." <> ...}

     

       23
       +
       ```

     

       24
       +
       

     

       25
       +
       ```elixir

     

       26
       +
       map =

     

       27
       +
         puzzle_input

     

       28
       +
         |> String.split("\n", trim: true)

     

       29
       +
         |> Enum.with_index()

     

       30
       +
         |> Enum.flat_map(fn {row, y} ->

     

       31
       +
           row

     

       32
       +
           |> String.to_charlist()

     

       33
       +
           |> Enum.with_index()

     

       34
       +
           |> Enum.map(fn {v, x} -> {{y, x}, v} end)

     

       35
       +
         end)

     

       36
       +
         |> Map.new()

     

       37
       +
       ```

     

       38
       +
       

     

       39
       +
       <!-- livebook:{"output":true} -->

     

       40
       +
       

     

       41
       +
       ```

     

       42
       +
       %{

     

       43
       +
         {18, 103} => 46,

     

       44
       +
         {76, 13} => 46,

     

       45
       +
         {61, 121} => 46,

     

       46
       +
         {37, 47} => 46,

     

       47
       +
         {65, 63} => 46,

     

       48
       +
         {77, 129} => 46,

     

       49
       +
         {120, 47} => 46,

     

       50
       +
         {38, 2} => 46,

     

       51
       +
         {1, 26} => 46,

     

       52
       +
         {116, 69} => 46,

     

       53
       +
         {124, 56} => 46,

     

       54
       +
         {83, 76} => 46,

     

       55
       +
         {117, 125} => 46,

     

       56
       +
         {32, 15} => 46,

     

       57
       +
         {103, 106} => 46,

     

       58
       +
         {30, 113} => 46,

     

       59
       +
         {123, 104} => 46,

     

       60
       +
         {124, 60} => 46,

     

       61
       +
         {89, 14} => 46,

     

       62
       +
         {35, 30} => 46,

     

       63
       +
         {37, 53} => 46,

     

       64
       +
         {4, 5} => 46,

     

       65
       +
         {8, 50} => 46,

     

       66
       +
         {78, 98} => 46,

     

       67
       +
         {101, 62} => 46,

     

       68
       +
         {95, 56} => 46,

     

       69
       +
         {74, 12} => 46,

     

       70
       +
         {102, 74} => 46,

     

       71
       +
         {11, 39} => 46,

     

       72
       +
         {65, 43} => 46,

     

       73
       +
         {22, 38} => 46,

     

       74
       +
         {14, 86} => 46,

     

       75
       +
         {49, 117} => 46,

     

       76
       +
         {20, 41} => 46,

     

       77
       +
         {29, 25} => 46,

     

       78
       +
         {86, 10} => 46,

     

       79
       +
         {83, 36} => 46,

     

       80
       +
         {29, 26} => 46,

     

       81
       +
         {47, 27} => 46,

     

       82
       +
         {4, 81} => 46,

     

       83
       +
         {31, 42} => 46,

     

       84
       +
         {9, 34} => 46,

     

       85
       +
         {13, 124} => 46,

     

       86
       +
         {90, 0} => 46,

     

       87
       +
         {14, 122} => 46,

     

       88
       +
         {120, 42} => 46,

     

       89
       +
         {121, 77} => 46,

     

       90
       +
         {103, 39} => 46,

     

       91
       +
         {102, ...} => 46,

     

       92
       +
         {...} => 46,

     

       93
       +
         ...

     

       94
       +
       }

     

       95
       +
       ```

     

       96
       +
       

     

       97
       +
       ```elixir

     

       98
       +
       {start_pos, _} = start = Enum.find(map, fn {_pos, v} -> v in ~c'^>v<' end)

     

       99
       +
       

     

       100
       +
       map = Map.replace(map, start_pos, ?.)

     

       101
       +
       

     

       102
       +
       start

     

       103
       +
       ```

     

       104
       +
       

     

       105
       +
       <!-- livebook:{"output":true} -->

     

       106
       +
       

     

       107
       +
       ```

     

       108
       +
       {{93, 71}, 94}

     

       109
       +
       ```

     

       110
       +
       

     

       111
       +
       ```elixir

     

       112
       +
       defmodule Guard do

     

       113
       +
         def walk(map, start),

     

       114
       +
           do: walk(map, start, MapSet.new())

     

       115
       +
       

     

       116
       +
         defp walk(map, {pos, dir} = curr, visited) do

     

       117
       +
           if curr in visited do

     

       118
       +
             :loop

     

       119
       +
           else

     

       120
       +
             visited = MapSet.put(visited, curr)

     

       121
       +
       

     

       122
       +
             case Map.fetch(map, next(pos, dir)) do

     

       123
       +
               {:ok, ?#} ->

     

       124
       +
                 walk(map, {pos, turn(dir)}, visited)

     

       125
       +
       

     

       126
       +
               {:ok, ?.} ->

     

       127
       +
                 walk(map, {next(pos, dir), dir}, visited)

     

       128
       +
       

     

       129
       +
               :error ->

     

       130
       +
                 MapSet.new(visited, fn {pos, _} -> pos end)

     

       131
       +
             end

     

       132
       +
           end

     

       133
       +
         end

     

       134
       +
       

     

       135
       +
         defp next({y, x}, ?^), do: {y - 1, x}

     

       136
       +
         defp next({y, x}, ?>), do: {y, x + 1}

     

       137
       +
         defp next({y, x}, ?v), do: {y + 1, x}

     

       138
       +
         defp next({y, x}, ?<), do: {y, x - 1}

     

       139
       +
       

     

       140
       +
         defp turn(?^), do: ?>

     

       141
       +
         defp turn(?>), do: ?v

     

       142
       +
         defp turn(?v), do: ?<

     

       143
       +
         defp turn(?<), do: ?^

     

       144
       +
       end

     

       145
       +
       ```

     

       146
       +
       

     

       147
       +
       <!-- livebook:{"output":true} -->

     

       148
       +
       

     

       149
       +
       ```

     

       150
       +
       {:module, Guard, <<70, 79, 82, 49, 0, 0, 12, ...>>, {:turn, 1}}

     

       151
       +
       ```

     

       152
       +
       

     

       153
       +
       ## Part 1

     

       154
       +
       

     

       155
       +
       ```elixir

     

       156
       +
       orig_path = Guard.walk(map, start)

     

       157
       +
         

     

       158
       +
       MapSet.size(orig_path)

     

       159
       +
       ```

     

       160
       +
       

     

       161
       +
       <!-- livebook:{"output":true} -->

     

       162
       +
       

     

       163
       +
       ```

     

       164
       +
       4433

     

       165
       +
       ```

     

       166
       +
       

     

       167
       +
       ## Part 2

     

       168
       +
       

     

       169
       +
       ```elixir

     

       170
       +
       orig_path

     

       171
       +
       |> MapSet.delete(start_pos)

     

       172
       +
       |> Task.async_stream(fn point ->

     

       173
       +
         map

     

       174
       +
         |> Map.put(point, ?#)

     

       175
       +
         |> Guard.walk(start)

     

       176
       +
         |> Kernel.==(:loop)

     

       177
       +
         end, ordered: false)

     

       178
       +
       |> Enum.count(& &1)

     

       179
       +
       ```

     

       180
       +
       

     

       181
       +
       <!-- livebook:{"output":true} -->

     

       182
       +
       

     

       183
       +
       ```

     

       184
       +
       4432

     

       185
       +
       ```

     

       186
       +
       

     

       187
       +
       <!-- livebook:{"offset":7387,"stamp":{"token":"XCP.Wj_YFc-zYzAPEIaLCGnT6vtMYoDgv-DJ3xiuAVdHZPkMwNpP5jrmLW4LBe4lzRgNN75xF-FYACOKdzd82Z71i5y8yC5Wmd072w6qDXxmygH8fZvTOAZM02UZvvg20b5Yhv0","version":2}} -->