solve 2021 day 10

2021/README.md

@@ -12,12 +12,12 @@
   ```
 </details>
 
-|  S  |  M  |  T  |  W  |  T  |  F  |  S  |
-| :-: | :-: | :-: | :-: | :-: | :-: | :-: |
-|     |     |     | [1] | [2] | [3] | [4] |
-| [5] | [6] | [7] | [8] | [9] | 10  | 11  |
-| 12  | 13  | 14  | 15  | 16  | 17  | 18  |
-| 19  | 20  | 21  | 22  | 23  | 24  | 25  |
+|  S  |  M  |  T  |  W  |  T  |  F   |  S  |
+| :-: | :-: | :-: | :-: | :-: | :-:  | :-: |
+|     |     |     | [1] | [2] | [3]  | [4] |
+| [5] | [6] | [7] | [8] | [9] | [10] | 11  |
+| 12  | 13  | 14  | 15  | 16  | 17   | 18  |
+| 19  | 20  | 21  | 22  | 23  | 24   | 25  |
 
 <!-- links -->
 
@@ -30,3 +30,4 @@
 [7]: ./lib/2021/7.ex
 [8]: ./lib/2021/8.ex
 [9]: ./lib/2021/9.ex
+[10]: ./lib/2021/10.ex

2021/lib/2021/10.ex

@@ -0,0 +1,76 @@
+import AOC
+
+aoc 2021, 10 do
+  @openers '([{<'
+  @closers ')]}>'
+
+  def points_for_invalid_char(?)), do: 3
+  def points_for_invalid_char(?]), do: 57
+  def points_for_invalid_char(?}), do: 1197
+  def points_for_invalid_char(?>), do: 25137
+
+  def points_for_missing_char(?)), do: 1
+  def points_for_missing_char(?]), do: 2
+  def points_for_missing_char(?}), do: 3
+  def points_for_missing_char(?>), do: 4
+
+  def pair_for(?(), do: ?)
+  def pair_for(?[), do: ?]
+  def pair_for(?{), do: ?}
+  def pair_for(?<), do: ?>
+
+  def find_line_errors(inp, state \\ [], inv \\ [])
+
+  def find_line_errors([], state, inv), do: {inv, state}
+
+  def find_line_errors([x | xs], [x | ys], inv), do: find_line_errors(xs, ys, inv)
+
+  def find_line_errors([x | xs], state, inv) when x in @closers,
+    do: find_line_errors(xs, Enum.drop(state, 1), [x | inv])
+
+  def find_line_errors([x | xs], ys, inv) when x in @openers,
+    do: find_line_errors(xs, [pair_for(x) | ys], inv)
+
+  def score_missing_charlist(charlist, score \\ 0)
+  def score_missing_charlist([], score), do: score
+
+  def score_missing_charlist([x | xs], score),
+    do: score_missing_charlist(xs, points_for_missing_char(x) + score * 5)
+
+  def input_charlist_stream(), do: input_stream() |> Stream.map(&String.to_charlist/1)
+
+  def invalid_chars_stream(),
+    do:
+      input_charlist_stream()
+      |> Stream.map(&find_line_errors/1)
+      |> Stream.reject(&match?({[], _}, &1))
+      |> Stream.map(&elem(&1, 0))
+      |> Stream.map(&hd/1)
+
+  def missing_charlists_stream(),
+    do:
+      input_charlist_stream()
+      |> Stream.map(&find_line_errors/1)
+      |> Stream.filter(&match?({[], _}, &1))
+      |> Stream.reject(&match?({_, []}, &1))
+      |> Stream.map(&elem(&1, 1))
+
+  def p1 do
+    invalid_chars_stream()
+    |> Stream.map(&points_for_invalid_char/1)
+    |> Enum.sum()
+  end
+
+  def p2 do
+    scores =
+      missing_charlists_stream()
+      |> Stream.map(&score_missing_charlist/1)
+      |> Enum.sort()
+
+    scores_count = length(scores)
+
+    winner = scores |> Enum.at(div(scores_count, 2))
+
+    winner
+  end
+end

2021/mix.exs

@@ -29,7 +29,8 @@ defmodule AdventOfCode.MixProject do
       {:benchee, "~> 1.0", only: :dev},
       {:exla, "~> 0.1.0-dev", github: "elixir-nx/nx", sparse: "exla"},
       {:nimble_parsec, "~> 1.0"},
-      {:nx, "~> 0.1.0-dev", github: "elixir-nx/nx", sparse: "nx", override: true}
+      {:nx, "~> 0.1.0-dev", github: "elixir-nx/nx", sparse: "nx", override: true},
+      {:rexbug, ">= 1.0.0"}
     ]
   end
 end

2021/mix.lock

@@ -15,6 +15,8 @@
   "nimble_pool": {:hex, :nimble_pool, "0.2.4", "1db8e9f8a53d967d595e0b32a17030cdb6c0dc4a451b8ac787bf601d3f7704c3", [:mix], [], "hexpm", "367e8071e137b787764e6a9992ccb57b276dc2282535f767a07d881951ebeac6"},
   "nx": {:git, "https://github.com/elixir-nx/nx.git", "e23a678bf0ebcbbafe03f1b5ed78623f052ad486", [sparse: "nx"]},
   "progress_bar": {:hex, :progress_bar, "2.0.1", "7b40200112ae533d5adceb80ff75fbe66dc753bca5f6c55c073bfc122d71896d", [:mix], [{:decimal, "~> 2.0", [hex: :decimal, repo: "hexpm", optional: false]}], "hexpm", "2519eb58a2f149a3a094e729378256d8cb6d96a259ec94841bd69fdc71f18f87"},
+  "redbug": {:hex, :redbug, "1.2.2", "366d8961770ddc7bb5d209fbadddfa7271005487f938c087a0e385a57abfee33", [:rebar3], [], "hexpm", "b5fe7b94e487be559cb0ec1c0e938c9761205d3e91a96bf263bdf1beaebea729"},
+  "rexbug": {:hex, :rexbug, "1.0.5", "e4fce59d1cb4f574b2d84181507b4782bc4b6afcb64e2cd276003c563ffef766", [:mix], [{:mix_test_watch, ">= 0.5.0", [hex: :mix_test_watch, repo: "hexpm", optional: true]}, {:redbug, "~> 1.2", [hex: :redbug, repo: "hexpm", optional: false]}], "hexpm", "13a3f180a9e490686a774725a07a21caf05735b7c012824d86960e9541aab46a"},
   "telemetry": {:hex, :telemetry, "1.0.0", "0f453a102cdf13d506b7c0ab158324c337c41f1cc7548f0bc0e130bbf0ae9452", [:rebar3], [], "hexpm", "73bc09fa59b4a0284efb4624335583c528e07ec9ae76aca96ea0673850aec57a"},
   "typed_struct": {:hex, :typed_struct, "0.2.1", "e1993414c371f09ff25231393b6430bd89d780e2a499ae3b2d2b00852f593d97", [:mix], [], "hexpm", "8f5218c35ec38262f627b2c522542f1eae41f625f92649c0af701a6fab2e11b3"},
   "xla": {:hex, :xla, "0.2.0", "689887888afb22587168d461f0e9ff83d7b06040273ea7082dbf9ff7eca33dcc", [:make, :mix], [{:elixir_make, "~> 0.4", [hex: :elixir_make, repo: "hexpm", optional: false]}], "hexpm", "a2e7b81413db49a159eabfb12dbd784a7c04b5c68c7b4057238d5ec9b110f2ec"},