2024 day 19 part 2

README.md

@@ -5,8 +5,8 @@
 My Elixir solutions for [Advent of Code](https://adventofcode.com/) (all years).
 
 <!-- stars start -->
-<p><img src="https://img.shields.io/static/v1?label=Total&message=454%20stars&style=for-the-badge&color=green" alt="454 stars" /></p>
-<p><a href="./lib/y2024/"><img src="https://img.shields.io/static/v1?label=2024&message=35%20stars&style=for-the-badge&color=yellow" alt="35 stars" /></a><br />
+<p><img src="https://img.shields.io/static/v1?label=Total&message=455%20stars&style=for-the-badge&color=green" alt="455 stars" /></p>
+<p><a href="./lib/y2024/"><img src="https://img.shields.io/static/v1?label=2024&message=36%20stars&style=for-the-badge&color=yellow" alt="36 stars" /></a><br />
 <a href="./lib/y2023/"><img src="https://img.shields.io/static/v1?label=2023&message=44%20stars&style=for-the-badge&color=green" alt="44 stars" /></a><br />
 <a href="./lib/y2022/"><img src="https://img.shields.io/static/v1?label=2022&message=%E2%AD%90%EF%B8%8F%2050%20stars%20%E2%AD%90%EF%B8%8F&style=for-the-badge&color=brightgreen" alt="50 stars" /></a><br />
 <a href="./lib/y2021/"><img src="https://img.shields.io/static/v1?label=2021&message=46%20stars&style=for-the-badge&color=green" alt="46 stars" /></a><br />

lib/y2024/README.md

@@ -2,7 +2,7 @@
 
 My Elixir solutions for [Advent of Code 2024](https://adventofcode.com/2024).
 
-<!-- stars 2024 start --><img src="https://img.shields.io/static/v1?label=2024&message=35%20stars&style=for-the-badge&color=yellow" alt="35 stars" /><!-- stars 2024 end -->
+<!-- stars 2024 start --><img src="https://img.shields.io/static/v1?label=2024&message=36%20stars&style=for-the-badge&color=yellow" alt="36 stars" /><!-- stars 2024 end -->
 
 ## Benchmarks
 
@@ -48,5 +48,6 @@ day 16, part 2         13.07       76.51 ms     ±5.00%       76.09 ms       85.
 day 17, part 1       45.64 K       21.91 μs    ±15.81%       21.17 μs       37.50 μs
 day 18, part 1         22.53       44.38 ms     ±5.11%       44.48 ms       48.54 ms
 day 18, part 2          4.04      247.58 ms     ±3.18%      247.68 ms      260.90 ms
-day 19, part 1         19.46       51.38 ms     ±1.08%       51.16 ms       53.08 ms
+day 19, part 1          4.30      232.82 ms     ±1.78%      230.67 ms      240.83 ms
+day 19, part 2          4.31      232.07 ms     ±0.63%      231.50 ms      236.27 ms
 ```

lib/y2024/day19.ex

@@ -3,43 +3,61 @@ defmodule Y2024.Day19 do
 
   def part1(%{from: from_towels, to: to_towels}) do
     Enum.count(to_towels, fn to ->
-      can_make?(to, from_towels)
+      ways_to_make(to, from_towels) != 0
     end)
   end
 
-  # @doc """
-  # iex> Day19.part2("update or delete me")
-  # "update or delete me"
-  # """
-  # def part2(input) do
-  #   input
-  # end
+  def part2(%{from: from_towels, to: to_towels}) do
+    Enum.map(to_towels, fn to ->
+      ways_to_make(to, from_towels)
+    end)
+    |> Enum.sum()
+  end
 
-  defp can_make?(to, from_towels) do
-    find_towel_list([{to, []}], from_towels) != nil
+  def ways_to_make(to, from_towels) do
+    queue = add_to_queue(PriorityQueue.new(), to)
+    find_towel_list(queue, from_towels, %{})
   end
 
-  defp find_towel_list([], _from_towels), do: nil
-  defp find_towel_list([{[], made} | _rest], _from_towels), do: Enum.reverse(made)
+  defp add_to_queue(queue, item) do
+    PriorityQueue.push(queue, item, -String.length(item))
+  end
 
-  defp find_towel_list([{to, made} | rest], from_towels) do
-    new =
-      from_towels
-      |> Enum.filter(fn from -> List.starts_with?(to, from) end)
-      |> Enum.map(fn from -> {Enum.drop(to, length(from)), [from | made]} end)
+  def find_towel_list(queue, from_towels, seen) do
+    do_find_towel_list(PriorityQueue.pop(queue), from_towels, seen)
+  end
+
+  defp do_find_towel_list({:empty, _queue}, _from_towels, _seen), do: 0
 
-    find_towel_list(new ++ rest, from_towels)
+  defp do_find_towel_list({{:value, ""}, _queue}, _from_towels, seen), do: Map.fetch!(seen, "")
+
+  defp do_find_towel_list({{:value, to}, queue}, from_towels, seen) do
+    {seen, queue} =
+      from_towels
+      |> Enum.filter(fn from -> String.starts_with?(to, from) end)
+      |> Enum.reduce({seen, queue}, fn from, {seen, queue} ->
+        rest = String.slice(to, String.length(from), 1000)
+        to_count = Map.get(seen, to, 1)
+
+        if Map.has_key?(seen, rest) do
+          {Map.update!(seen, rest, &(&1 + to_count)), queue}
+        else
+          {Map.put(seen, rest, to_count), add_to_queue(queue, rest)}
+        end
+      end)
+
+    find_towel_list(queue, from_towels, seen)
   end
 
   def parse_input(input) do
     [from, to] = String.split(input, "\n\n", trim: true)
 
     %{
-      from: String.split(from, ", ") |> Enum.map(&String.graphemes/1),
-      to: String.split(to, "\n", trim: true) |> Enum.map(&String.graphemes/1)
+      from: String.split(from, ", "),
+      to: String.split(to, "\n", trim: true)
     }
   end
 
   def part1_verify, do: input() |> parse_input() |> part1()
-  # def part2_verify, do: input() |> parse_input() |> part2()
+  def part2_verify, do: input() |> parse_input() |> part2()
 end

test/y2024/day19_test.exs

@@ -20,12 +20,16 @@ defmodule Y2024.Day19Test do
     assert Day19.parse_input(@sample) |> Day19.part1() == 6
   end
 
+  test "part2" do
+    assert Day19.parse_input(@sample) |> Day19.part2() == 16
+  end
+
   test "parse_input" do
     assert %{from: from, to: to} = Day19.parse_input(@sample)
-    assert [["r"], ["w", "r"] | _rest] = from
-    assert [["b", "r", "w", "r", "r"], ["b", "g", "g", "r"] | _rest] = to
+    assert ["r", "wr" | _rest] = from
+    assert ["brwrr", "bggr" | _rest] = to
   end
 
   test "verification, part 1", do: assert(Day19.part1_verify() == 285)
-  # test "verification, part 2", do: assert(Day19.part2_verify() == "update or delete me")
+  test "verification, part 2", do: assert(Day19.part2_verify() == 636_483_903_099_279)
 end