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hauleth.dev
1<!-- livebook:{"persist_outputs":true} -->
2
3# Day 10
4
5```elixir
6Mix.install([:kino_aoc])
7```
8
9## Section
10
11<!-- livebook:{"attrs":"eyJhc3NpZ25fdG8iOiJwdXp6bGVfaW5wdXQiLCJkYXkiOiIxMCIsInNlc3Npb25fc2VjcmV0IjoiQURWRU5UX09GX0NPREVfU0VTU0lPTiIsInllYXIiOiIyMDI0In0","chunks":null,"kind":"Elixir.KinoAOC.HelperCell","livebook_object":"smart_cell"} -->
12
13```elixir
14{:ok, puzzle_input} =
15 KinoAOC.download_puzzle("2024", "10", System.fetch_env!("LB_ADVENT_OF_CODE_SESSION"))
16```
17
18<!-- livebook:{"output":true} -->
19
20```
21{:ok,
22 "543067650323210321032110356789890110710189878760134567\n612148941212306782345091235410765227893258759651021298\n701238932301456798106787549323454336794567549842330807\n898547215450589867287654678892961245987654456732498910\n987656306769678956398013234781870301256003301201567821\n234543215878760145478920105690210982340112210341056932\n109650124981232230569834124567345673451234985452347845\n018744323890341021656765033438454589298545676701037796\n199803210787650110765017842129823672107655677812378987\n785012345654789541874326956010510563201234389983405676\n174321498723498632903455467173421454102348210234514430\n065430239014323721212762398982567876218959650149623521\n145540128765017890101871081071018967327968743898734678\n236692134984178768718981012567894458456876212798604329\n987783005673269659654108923458763349663212108789015012\n896654012562154546743267830309854218767103419276126787\n765780123473043432890154321212903109878756578125435698\n434099874984012301740125654567812893469017647030165556\n323101065765101787434436763058906732154178736543256765\n013298187890678696325569892143215440043289128954343894\n010367296541549045016678765014300351234567037760012983\n329458305032132134787867410967891267653438546891898012\n458789414145010120196986323898763298344129655432743210\n567076523236678743285898456777654101201098766653658901\n456167654107549658374567689985403100312434985567877014\n343228943298938569843210576876312238920125676656986323\n651014543498127478755765435410278947437876985543235434\n743223672567078369876890324320127656506987234350145632\n894102981089569232125981210451256543215432122341076541\n765091234676352101034674323401237894101341001456789830\n014780365445443032126501012532345743103210112565898321\n123689876034321145098432107645236743254101101876543210\n094545763125210056788943258896107858969010332987674301\n785430432106782169877652349787567967678321245696784561\n876021569045893458965601654343478914565414326781093870\n987109878010432167014298710234323901258905015492012901\n789219894324569052123109620123217892109876012323458692\n654308765543678743013234538994106543010870965410069783\n789877787632189852101110145885287676521961871012178654\n034565896601087601211001406776896789437652676523468743\n121053795542194512389132312345445676548943989430549012\n262342187634765433498545434531230107401232104321678298\n876533014123892324567696526540043298340981010780890187\n983414523016101019876587017832134781256672125690743296\n032101654327892100345678789901295690764543434321652345\n123089789236743981234589654800387789835678987787601336\n854176590187656876104310343211456876544549016098543223\n965765410194545675465231230898565963233432145123210112\n876894321243232980370110141767653210112321039654101101\n146765232100101061289879852632154100203410128789210322\n036787103761267876518768763543069911012543454376325412\n123498654854356987405650654985678892327632567215436701\n210567569983543292314321569876301765438761078904589898\n325456478754330101223433478765432654349652987615678765"}
23```
24
25```elixir
26map =
27 for {row, y} <- puzzle_input |> String.split("\n", trim: true) |> Enum.with_index(),
28 {h, x} <- row |> String.to_charlist() |> Enum.with_index(),
29 into: %{},
30 do: {{x, y}, h - ?0}
31```
32
33<!-- livebook:{"output":true} -->
34
35```
36%{
37 {37, 47} => 3,
38 {38, 2} => 4,
39 {1, 26} => 5,
40 {32, 15} => 4,
41 {35, 30} => 3,
42 {37, 53} => 4,
43 {4, 5} => 4,
44 {8, 50} => 3,
45 {11, 39} => 1,
46 {22, 38} => 1,
47 {20, 41} => 8,
48 {29, 25} => 6,
49 {29, 26} => 0,
50 {47, 27} => 0,
51 {31, 42} => 4,
52 {9, 34} => 0,
53 {47, 38} => 2,
54 {20, 3} => 7,
55 {47, 44} => 1,
56 {22, 37} => 3,
57 {22, 36} => 0,
58 {45, 7} => 7,
59 {19, 38} => 0,
60 {27, 21} => 9,
61 {9, 33} => 1,
62 {26, 41} => 4,
63 {52, 42} => 8,
64 {21, 35} => 2,
65 {42, 8} => 6,
66 {19, 22} => 9,
67 {16, 10} => 3,
68 {21, 45} => 5,
69 {11, 8} => 7,
70 {26, 21} => 0,
71 {21, 48} => 1,
72 {50, 40} => 9,
73 {10, 25} => 9,
74 {11, 19} => 0,
75 {16, 38} => 5,
76 {35, 15} => 8,
77 {37, 15} => 6,
78 {35, 26} => 7,
79 {28, 20} => 1,
80 {45, 19} => 9,
81 {27, 22} => 8,
82 {16, 24} => 5,
83 {6, 18} => 0,
84 {10, 32} => 2,
85 {32, ...} => 8,
86 {...} => 7,
87 ...
88}
89```
90
91```elixir
92starts = Enum.filter(map, fn {_, elev} -> elev == 0 end)
93```
94
95<!-- livebook:{"output":true} -->
96
97```
98[
99 {{38, 5}, 0},
100 {{24, 7}, 0},
101 {{11, 35}, 0},
102 {{3, 9}, 0},
103 {{15, 36}, 0},
104 {{41, 32}, 0},
105 {{51, 14}, 0},
106 {{51, 24}, 0},
107 {{5, 12}, 0},
108 {{4, 35}, 0},
109 {{40, 4}, 0},
110 {{46, 4}, 0},
111 {{22, 30}, 0},
112 {{27, 12}, 0},
113 {{7, 4}, 0},
114 {{24, 43}, 0},
115 {{31, 20}, 0},
116 {{29, 42}, 0},
117 {{29, 9}, 0},
118 {{10, 2}, 0},
119 {{0, 20}, 0},
120 {{15, 20}, 0},
121 {{14, 0}, 0},
122 {{42, 48}, 0},
123 {{40, 15}, 0},
124 {{43, 14}, 0},
125 {{19, 2}, 0},
126 {{14, 22}, 0},
127 {{34, 35}, 0},
128 {{38, 42}, 0},
129 {{23, 5}, 0},
130 {{0, 11}, 0},
131 {{44, 11}, 0},
132 {{15, 30}, 0},
133 {{17, 44}, 0},
134 {{31, 32}, 0},
135 {{48, 28}, 0},
136 {{21, 39}, 0},
137 {{49, 13}, 0},
138 {{29, 45}, 0},
139 {{4, 37}, 0},
140 {{53, 31}, 0},
141 {{45, 46}, 0},
142 {{43, 29}, 0},
143 {{8, 0}, 0},
144 {{47, 42}, 0},
145 {{7, 14}, 0},
146 {{52, ...}, 0},
147 {{...}, ...},
148 {...},
149 ...
150]
151```
152
153```elixir
154defmodule Trail do
155 def traverse(start, map), do: MapSet.new(traverse(start, map, []))
156
157 defp traverse({curr, 9}, _map, acc), do: [[{curr, 9} | acc]]
158 defp traverse({curr, elev}, map, acc) do
159 curr
160 |> surroundings()
161 |> then(&Map.take(map, &1))
162 |> Enum.filter(fn {_, h} -> elev + 1 == h end)
163 |> Enum.flat_map(&traverse(&1, map, [{curr, elev} | acc]))
164 end
165
166 defp surroundings({x, y}) do
167 [
168 {x, y - 1},
169 {x - 1, y},
170 {x, y + 1},
171 {x + 1, y}
172 ]
173 end
174end
175```
176
177<!-- livebook:{"output":true} -->
178
179```
180{:module, Trail, <<70, 79, 82, 49, 0, 0, 11, ...>>, {:surroundings, 1}}
181```
182
183## Part 1
184
185```elixir
186starts
187|> Enum.map(fn start ->
188 Trail.traverse(start, map)
189 |> MapSet.new(&hd/1)
190 |> MapSet.size()
191end)
192|> Enum.sum()
193```
194
195<!-- livebook:{"output":true} -->
196
197```
198733
199```
200
201## Section
202
203```elixir
204starts
205|> Enum.map(fn start ->
206 Trail.traverse(start, map)
207 |> MapSet.size()
208end)
209|> Enum.sum()
210```
211
212<!-- livebook:{"output":true} -->
213
214```
2151514
216```
217
218<!-- livebook:{"offset":6605,"stamp":{"token":"XCP.68U6SzidJCV7il26kiMv6z5qLEx_50_v2V7x6LqV9t8LQG1-aShVMNE1DEgCj9SwpKOn02np0aeSu5T1parIYMF9MeWGGfqP-oc4UGnDiDGDtJ5RGqdwcxcPjuPUQmCtZj0","version":2}} -->