feat: Create initial files for Advent of Code 2024 Day 3 solution

lib/advent_code2024/solutions/day03/day3.ex

@@ -0,0 +1,59 @@
+defmodule AdventCode2024.Solutions.Day03 do
+  @moduledoc """
+  Solution for Advent of Code 2024, Day 3
+  """
+
+  @behaviour AdventCode2024.Solution
+
+  @default_input "lib/advent_code2024/solutions/day03/input.txt"
+
+  @doc """
+  Solve part 1 of the challenge
+  """
+  def solve(input \\ @default_input)
+  def solve(""), do: {:error, :no_input}
+  def solve(input) when is_binary(input) and input != "" do
+    if String.contains?(input, "\n") or !String.contains?(input, "/") do
+      # Input is content
+      solve_content(input)
+    else
+      # Input is file path
+      case File.read(input) do
+        {:ok, content} -> solve_content(content)
+        {:error, reason} -> {:error, reason}
+      end
+    end
+  end
+
+  @doc """
+  Solve part 2 of the challenge
+  """
+  def solve_part2(input \\ @default_input)
+  def solve_part2(""), do: {:error, :no_input}
+  def solve_part2(input) when is_binary(input) and input != "" do
+    if String.contains?(input, "\n") or !String.contains?(input, "/") do
+      # Input is content
+      solve_part2_content(input)
+    else
+      # Input is file path
+      case File.read(input) do
+        {:ok, content} -> solve_part2_content(content)
+        {:error, reason} -> {:error, reason}
+      end
+    end
+  end
+
+  # Private functions
+
+  defp solve_content(""), do: {:error, :no_input}
+  defp solve_content(content) when is_binary(content) and content != "" do
+    # TODO: Implement solution for part 1
+    {:ok, 0}
+  end
+
+  defp solve_part2_content(""), do: {:error, :no_input}
+  defp solve_part2_content(content) when is_binary(content) and content != "" do
+    # TODO: Implement solution for part 2
+    {:ok, 0}
+  end
+end

lib/advent_code2024/solutions/day03/input.txt

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+# Add your puzzle input here

test/advent_code2024/solutions/day03/day3_test.exs

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+defmodule AdventCode2024.Solutions.Day03Test do
+  use ExUnit.Case
+  alias AdventCode2024.Solutions.Day03
+
+  describe "solve/1" do
+    test "returns error for empty input" do
+      assert Day03.solve("") == {:error, :no_input}
+    end
+
+    test "returns error for invalid file" do
+      assert Day03.solve("nonexistent.txt") == {:error, :enoent}
+    end
+
+    # TODO: Add more specific tests for part 1
+  end
+
+  describe "solve_part2/1" do
+    test "returns error for empty input" do
+      assert Day03.solve_part2("") == {:error, :no_input}
+    end
+
+    test "returns error for invalid file" do
+      assert Day03.solve_part2("nonexistent.txt") == {:error, :enoent}
+    end
+
+    # TODO: Add more specific tests for part 2
+  end
+end