Finished day 8

README.org

@@ -18,4 +18,5 @@ Day 6: [[https://livebook.dev/run?url=https%3A%2F%2Fgit.datarift.nl%2Ferwin%2Fao
 
 Day 7: [[https://livebook.dev/run?url=https%3A%2F%2Fgit.datarift.nl%2Ferwin%2Faoc2022%2Fraw%2Fbranch%2Fmain%2Fday7.livemd][Run in Livebook]]
 
+Day 8: [[https://livebook.dev/run?url=https%3A%2F%2Fgit.datarift.nl%2Ferwin%2Faoc2022%2Fraw%2Fbranch%2Fmain%2Fday8.livemd][Run in Livebook]]
 

day8.livemd

@@ -0,0 +1,276 @@
+# AOC 2022 - Day 8
+
+```elixir
+Mix.install(
+  [
+    {:req, "~> 0.3.3"},
+    {:nx, "~> 0.4.1"},
+    {:exla, "~> 0.4.1"}
+  ],
+  config: [nx: [default_backend: EXLA.Backend]]
+)
+```
+
+## Puzzle description
+
+[Day 8: Treetop Tree House](https://adventofcode.com/2022/day/8).
+
+## Input
+
+```elixir
+defmodule Load do
+  def input do
+    aoc_session = System.fetch_env!("LB_AOC_SESSION")
+    input_url = "https://adventofcode.com/2022/day/8/input"
+    Req.get!(input_url, headers: [cookie: "session=#{aoc_session}"]).body
+  end
+end
+```
+
+## Solution
+
+```elixir
+defmodule Util do
+  def process(input) do
+    input
+    |> String.split("\n", trim: true)
+    |> Enum.map(fn row ->
+      row
+      |> String.split("", trim: true)
+      |> Enum.map(&String.to_integer/1)
+    end)
+  end
+
+  def process2(input) do
+    input
+    |> String.split()
+    |> Enum.with_index()
+    |> Enum.flat_map(&parse_line/1)
+    |> Map.new(fn {v, k} -> {k, v} end)
+  end
+
+  defp parse_line({string, row}) do
+    string
+    |> String.graphemes()
+    |> Enum.with_index()
+    |> Enum.map(fn {char, column} ->
+      {String.to_integer(char), {row + 1, column + 1}}
+    end)
+  end
+
+  def count_visible(line) do
+    line
+    |> Enum.with_index()
+    |> Enum.map_reduce(0, fn {h, n}, max ->
+      cond do
+        n == 0 ->
+          {true, h}
+
+        h <= max ->
+          {false, max}
+
+        true ->
+          {true, h}
+      end
+    end)
+    |> elem(0)
+  end
+
+  def transpose(v) do
+    v
+    |> List.zip()
+    |> Enum.map(&Tuple.to_list/1)
+  end
+
+  def score(trees, row, column, rows, columns) do
+    left_score(trees, row, column, rows, columns) *
+      right_score(trees, row, column, rows, columns) *
+      up_score(trees, row, column, rows, columns) *
+      down_score(trees, row, column, rows, columns)
+  end
+
+  defp left_score(trees, row, column, _rows, _columns) do
+    list =
+      for c <- (column - 1)..1 do
+        trees[{row, c}]
+      end
+      |> Enum.with_index()
+
+    len = length(list)
+
+    list
+    |> Enum.reduce_while(1, fn {height, position}, score ->
+      if trees[{row, column}] > height and position + 1 != len,
+        do: {:cont, score + 1},
+        else: {:halt, score}
+    end)
+  end
+
+  defp right_score(trees, row, column, _rows, columns) do
+    list =
+      for c <- (column + 1)..columns do
+        trees[{row, c}]
+      end
+      |> Enum.with_index()
+
+    len = length(list)
+
+    list
+    |> Enum.reduce_while(1, fn {height, position}, score ->
+      if trees[{row, column}] > height and position + 1 != len,
+        do: {:cont, score + 1},
+        else: {:halt, score}
+    end)
+  end
+
+  defp up_score(trees, row, column, _rows, _columns) do
+    list =
+      for r <- (row - 1)..1 do
+        trees[{r, column}]
+      end
+      |> Enum.with_index()
+
+    len = length(list)
+
+    list
+    |> Enum.reduce_while(1, fn {height, position}, score ->
+      if trees[{row, column}] > height and position + 1 != len,
+        do: {:cont, score + 1},
+        else: {:halt, score}
+    end)
+  end
+
+  defp down_score(trees, row, column, rows, _columns) do
+    list =
+      for r <- (row + 1)..rows do
+        trees[{r, column}]
+      end
+      |> Enum.with_index()
+
+    len = length(list)
+
+    list
+    |> Enum.reduce_while(1, fn {height, position}, score ->
+      if trees[{row, column}] > height and position + 1 != len,
+        do: {:cont, score + 1},
+        else: {:halt, score}
+    end)
+  end
+end
+```
+
+```elixir
+defmodule Part1 do
+  def run(input) do
+    trees =
+      input
+      |> Util.process()
+
+    {trees, horizontal} =
+      trees
+      |> Enum.map_reduce([], fn line, acc ->
+        visible =
+          [
+            Util.count_visible(line),
+            line |> Enum.reverse() |> Util.count_visible() |> Enum.reverse()
+          ]
+          |> Enum.zip()
+          |> Enum.map(&(elem(&1, 0) or elem(&1, 1)))
+
+        {line, [visible | acc]}
+      end)
+      |> then(fn {trees, horizontal} ->
+        {trees, Enum.reverse(horizontal)}
+      end)
+
+    {_, vertical} =
+      trees
+      |> Util.transpose()
+      |> Enum.map_reduce([], fn col, acc ->
+        visible =
+          [
+            Util.count_visible(col),
+            col |> Enum.reverse() |> Util.count_visible() |> Enum.reverse()
+          ]
+          |> Enum.zip()
+          |> Enum.map(&(elem(&1, 0) or elem(&1, 1)))
+
+        {col, [visible | acc]}
+      end)
+      |> then(fn {trees, vertical} ->
+        {trees, Enum.reverse(vertical) |> Util.transpose()}
+      end)
+
+    horizontal
+    |> Enum.zip(vertical)
+    |> Enum.map(fn {h, v} ->
+      h
+      |> Enum.zip(v)
+      |> Enum.map(&(elem(&1, 0) or elem(&1, 1)))
+    end)
+    |> Enum.map(fn line ->
+      Enum.count(line, & &1)
+    end)
+    |> Enum.sum()
+  end
+end
+
+defmodule Part2 do
+  def run(input) do
+    trees = Util.process2(input)
+
+    {rows, columns} =
+      trees
+      |> Map.keys()
+      |> Enum.max()
+
+    for i <- 2..(rows - 1), j <- 2..(columns - 1) do
+      {i, j, Util.score(trees, i, j, rows, columns)}
+    end
+    |> Enum.max_by(fn {_, _, x} -> x end)
+    |> elem(2)
+  end
+end
+
+ExUnit.start(autorun: false)
+
+defmodule Test do
+  use ExUnit.Case, async: true
+  @example_input ~s(30373
+25512
+65332
+33549
+35390)
+  @input Load.input()
+
+  test "it loads the input" do
+    assert String.length(@input) > 0
+  end
+
+  test "part 1 example" do
+    assert Part1.run(@example_input) === 21
+  end
+
+  test "part 1" do
+    assert Part1.run(@input) === 1816
+  end
+
+  test "part 2 example" do
+    assert Part2.run(@example_input) === 8
+  end
+
+  test "part 2" do
+    assert Part2.run(@input) === 0
+  end
+end
+
+ExUnit.run()
+
+# [
+#    [1, 1, 1, 1, 1],
+#    [1, 1, 1, 0, 1],
+#    [1, 1, 0, 1, 1],
+#    [1, 0, 1, 0, 1],
+#    [1, 1, 1, 1, 1]
+#  ]
+```

devshell.toml

@@ -4,6 +4,7 @@ packages = [
   "libnotify",
   "inotify-tools",
   "gnumake",
+  "gcc",
   "taplo",
 ]
 
@@ -55,3 +56,8 @@ value = "9091"
 name = "mix"
 package = "elixir_1_14"
 help = "mix"
+
+[[commands]]
+name = "livebook"
+command = "livebook $@"
+help = "livebook"

flake.lock

@@ -10,11 +10,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1667210711,
-        "narHash": "sha256-IoErjXZAkzYWHEpQqwu/DeRNJGFdR7X2OGbkhMqMrpw=",
+        "lastModified": 1671489820,
+        "narHash": "sha256-qoei5HDJ8psd1YUPD7DhbHdhLIT9L2nadscp4Qk37uk=",
         "owner": "numtide",
         "repo": "devshell",
-        "rev": "96a9dd12b8a447840cc246e17a47b81a4268bba7",
+        "rev": "5aa3a8039c68b4bf869327446590f4cdf90bb634",
         "type": "github"
       },
       "original": {
@@ -56,11 +56,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1670597555,
-        "narHash": "sha256-/k939P2S2246G6K5fyvC0U2IWvULhb4ZJg9K7ZxsX+k=",
+        "lastModified": 1672350804,
+        "narHash": "sha256-jo6zkiCabUBn3ObuKXHGqqORUMH27gYDIFFfLq5P4wg=",
         "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "2dea0f4c2d6e4603f54b2c56c22367e77869490c",
+        "rev": "677ed08a50931e38382dbef01cba08a8f7eac8f6",
         "type": "github"
       },
       "original": {