feat: pass the tests

lib/advent_code2024/solutions/day05/day5.ex

@@ -1,4 +1,4 @@
-defmodule AdventCode2024.Solutions.Day5 do
+defmodule AdventCode2024.Solutions.Day05 do
   @moduledoc """
   Day 5: Solution for Advent of Code 2024
   """
@@ -38,9 +38,13 @@ defmodule AdventCode2024.Solutions.Day5 do
   defp solve_content(""), do: {:error, :no_input}
 
   defp solve_content(content) when is_binary(content) and content != "" do
+    {rules, updates} = parse_input(content)
+
     result =
-      content
-      |> parse_input()
+      updates
+      |> Enum.filter(&is_valid_update?(&1, rules))
+      |> Enum.map(&get_middle_number/1)
+      |> Enum.sum()
 
     {:ok, result}
   end
@@ -56,7 +60,56 @@ defmodule AdventCode2024.Solutions.Day5 do
   end
 
   defp parse_input(input) do
-    input
+    [rules_section, updates_section] = String.split(input, "\n\n", trim: true)
+
+    rules = parse_rules(rules_section)
+    updates = parse_updates(updates_section)
+
+    {rules, updates}
+  end
+
+  defp parse_rules(rules_section) do
+    rules_section
     |> String.split("\n", trim: true)
+    |> Enum.map(fn rule ->
+      [first, second] = String.split(rule, "|")
+      {String.to_integer(first), String.to_integer(second)}
+    end)
+  end
+
+  defp parse_updates(updates_section) do
+    updates_section
+    |> String.split("\n", trim: true)
+    |> Enum.map(fn update ->
+      update
+      |> String.split(",", trim: true)
+      |> Enum.map(&String.to_integer/1)
+    end)
+  end
+
+  defp is_valid_update?(update, rules) do
+    # For each pair of numbers in the update, check if they satisfy all applicable rules
+    update
+    |> Enum.with_index()
+    |> Enum.all?(fn {num1, idx1} ->
+      update
+      |> Enum.with_index()
+      |> Enum.all?(fn {num2, idx2} ->
+        # Only check pairs where the second number comes after the first
+        if idx2 > idx1 do
+          # Check if there's a rule requiring num2 to come before num1
+          not Enum.any?(rules, fn {first, second} ->
+            num1 == second and num2 == first
+          end)
+        else
+          true
+        end
+      end)
+    end)
+  end
+
+  defp get_middle_number(update) do
+    middle_index = div(length(update), 2)
+    Enum.at(update, middle_index)
   end
 end

test/advent_code2024/solutions/day05/day5_test.exs

@@ -1,6 +1,6 @@
-defmodule AdventCode2024.Solutions.Day5Test do
+defmodule AdventCode2024.Solutions.Day05Test do
   use ExUnit.Case
-  alias AdventCode2024.Solutions.Day5
+  alias AdventCode2024.Solutions.Day05
 
   @example_input """
   47|53
@@ -33,17 +33,30 @@ defmodule AdventCode2024.Solutions.Day5Test do
   97,13,75,29,47
   """
 
+  setup_all do
+    # Create a temporary file for testing
+    path = "test/fixtures/day05/test_input.txt"
+    File.mkdir_p!(Path.dirname(path))
+    :ok = File.write(path, @example_input)
+
+    on_exit(fn ->
+      File.rm!(path)
+    end)
+
+    {:ok, test_file: path}
+  end
+
   describe "solve/1" do
-    test "correctly identifies valid updates and sums middle pages" do
-      assert {:ok, 143} = Day5.solve_content(@example_input)
+    test "correctly identifies valid updates and sums middle pages", %{test_file: path} do
+      assert {:ok, 143} = Day05.solve(path)
     end
 
     test "returns error for empty input" do
-      assert Day5.solve("") == {:error, :no_input}
+      assert Day05.solve("") == {:error, :no_input}
     end
 
     test "returns error for invalid file" do
-      assert Day5.solve("priv/nonexistent.txt") == {:error, :enoent}
+      assert Day05.solve("priv/nonexistent.txt") == {:error, :enoent}
     end
 
     test "validates first update is in correct order" do
@@ -61,7 +74,11 @@ defmodule AdventCode2024.Solutions.Day5Test do
 
       75,47,61,53,29
       """
-      assert {:ok, 61} = Day5.solve_content(input)
+
+      path = "test/fixtures/day05/first_update.txt"
+      :ok = File.write(path, input)
+      assert {:ok, 61} = Day05.solve(path)
+      File.rm!(path)
     end
 
     test "validates second update is in correct order" do
@@ -78,7 +95,11 @@ defmodule AdventCode2024.Solutions.Day5Test do
 
       97,61,53,29,13
       """
-      assert {:ok, 53} = Day5.solve_content(input)
+
+      path = "test/fixtures/day05/second_update.txt"
+      :ok = File.write(path, input)
+      assert {:ok, 53} = Day05.solve(path)
+      File.rm!(path)
     end
 
     test "identifies invalid update due to rule violation" do
@@ -87,7 +108,11 @@ defmodule AdventCode2024.Solutions.Day5Test do
 
       75,97,47,61,53
       """
-      assert {:ok, 0} = Day5.solve_content(input)
+
+      path = "test/fixtures/day05/invalid_update.txt"
+      :ok = File.write(path, input)
+      assert {:ok, 0} = Day05.solve(path)
+      File.rm!(path)
     end
   end
 end