day12

Author: akdemironur

12/sol.exs

@@ -0,0 +1,80 @@
+defmodule Day12 do
+  def read_input(file_path) do
+    case File.read(file_path) do
+      {:ok, content} ->
+        content
+        |> String.split("\n", trim: true)
+        |> Enum.map(&parse_line/1)
+
+      {:error, reason} ->
+        raise "Oh no! #{reason}"
+    end
+  end
+
+  def parse_line(line) do
+    [conditions, groups] = String.split(line, " ")
+    conditions = String.graphemes(conditions)
+    groups = String.split(groups, ",") |> Enum.map(&String.to_integer/1)
+    {conditions, groups}
+  end
+
+  def partA(file_path) do
+    read_input(file_path)
+    |> Enum.map(&solve(&1, %{}, 0, {0, 0, 0}))
+    |> Enum.map(&elem(&1, 1))
+    |> Enum.sum()
+  end
+
+  def partB(file_path) do
+    read_input(file_path)
+    |> Enum.map(fn {conditions, groups} ->
+      {conditions |> List.duplicate(5) |> Enum.intersperse("?") |> List.flatten(),
+       groups |> List.duplicate(5) |> List.flatten()}
+    end)
+    |> Enum.map(&solve(&1, %{}, 0, {0, 0, 0}))
+    |> Enum.map(&elem(&1, 1))
+    |> Enum.sum()
+  end
+
+  def solve(_, memo, _, key) when is_map_key(memo, key), do: {memo, memo[key]}
+
+  def solve({conditions, groups}, memo, acc, {id_conditions, id_groups, current_length})
+      when length(conditions) == id_conditions do
+    {memo,
+     case {current_length, length(groups), length(groups) - 1, Enum.at(groups, id_groups)} do
+       {0, ^id_groups, _, _} -> acc + 1
+       {_, _, ^id_groups, ^current_length} -> acc + 1
+       {_, _, _, _} -> acc
+     end}
+  end
+
+  def solve({conditions, groups}, memo, acc, key) do
+    {memo, acc}
+    |> solveH(".", conditions, groups, key)
+    |> solveH("#", conditions, groups, key)
+    |> (fn {memop, res} -> {Map.put(memop, key, res), res} end).()
+  end
+
+  def solveH({memo, acc}, c, conditions, groups, {id_conditions, id_groups, current_length}) do
+    cond do
+      (Enum.at(conditions, id_conditions) == c or Enum.at(conditions, id_conditions) == "?") and
+        c == "." and
+          current_length == 0 ->
+        solve({conditions, groups}, memo, 0, {id_conditions + 1, id_groups, 0})
+
+      (Enum.at(conditions, id_conditions) == c or Enum.at(conditions, id_conditions) == "?") and
+        c == "." and
+        current_length > 0 and length(groups) > id_groups and
+          Enum.at(groups, id_groups) == current_length ->
+        solve({conditions, groups}, memo, 0, {id_conditions + 1, id_groups + 1, 0})
+
+      (Enum.at(conditions, id_conditions) == c or Enum.at(conditions, id_conditions) == "?") and
+          c == "#" ->
+        solve({conditions, groups}, memo, 0, {id_conditions + 1, id_groups, current_length + 1})
+
+      true ->
+        {memo, 0}
+    end
+    |> (fn {memo, res} -> {memo, res + acc} end).()
+  end
+end