feat: pass examples for part2

fix: Refactor X-MAS pattern detection in Day04 solution

fix: Remove extra `end` in day4.ex module

lib/advent_code2024/solutions/day05/README.md

@@ -0,0 +1,111 @@
+# Day 5: Print Queue
+
+## Part 1
+
+Print the safety manual pages in the correct order.
+The notation X|Y means that if both page number X and page number Y are to be produced
+as part of an update, page number X must be printed at some point before page number Y.
+
+### Example
+
+The input contains both the page ordering rules and the pages to produce in each update.
+
+```txt
+47|53
+97|13
+97|61
+97|47
+75|29
+61|13
+75|53
+29|13
+97|29
+53|29
+61|53
+97|53
+61|29
+47|13
+75|47
+97|75
+47|61
+75|61
+47|29
+75|13
+53|13
+
+75,47,61,53,29
+97,61,53,29,13
+75,29,13
+75,97,47,61,53
+61,13,29
+97,13,75,29,47
+```
+
+The first section specifies the page ordering rules, one per line.
+The first rule, `47|53`, means that if an update includes both page number 47 and
+page number 53, then page number 47 must be printed at some point before page
+number 53. (47 doesn't necessarily need to be immediately before 53; other pages
+ are allowed to be between them.)
+
+The second section specifies the page numbers included in each update. Because most
+safety manuals are different, the pages needed in the updates are different too.
+The first update, `75,47,61,53,29`, means that the update consists of page
+numbers 75, 47, 61, 53, and 29.
+
+To get the printers going as soon as possible, start by identifying which updates
+ are already in the right order.
+
+In the above example, the first update (75,47,61,53,29) is in the right order:
+
+- 75 is correctly first because there are rules that put each other page after it: 75|47, 75|61, 75|53, and 75|29.
+- 47 is correctly second because 75 must be before it (75|47) and every other page must be after it according to 47|61, 47|53, and 47|29.
+- 61 is correctly in the middle because 75 and 47 are before it (75|61 and 47|61) and 53 and 29 are after it (61|53 and 61|29).
+- 53 is correctly fourth because it is before page number 29 (53|29).
+- 29 is the only page left and so is correctly last.
+
+Because the first update does not include some page numbers, the ordering rules
+involving those missing page numbers are ignored.
+
+The second and third updates are also in the correct order according to the rules.
+Like the first update, they also do not include every page number, and so only some
+of the ordering rules apply - within each update, the ordering rules that involve
+missing page numbers are not used.
+
+The fourth update, 75,97,47,61,53, is not in the correct order: it would print 75
+before 97, which violates the rule 97|75.
+
+The fifth update, 61,13,29, is also not in the correct order, since it breaks the
+rule 29|13.
+
+The last update, 97,13,75,29,47, is not in the correct order due to breaking
+several rules.
+
+For some reason, the Elves also need to know the middle page number of each update being printed. Because you are currently only printing the correctly-ordered updates, you will need to find the middle page number of each correctly-ordered update. In the above example, the correctly-ordered updates are:
+
+```txt
+75,47,61,53,29  
+97,61,53,29,13
+75,29,13
+```
+
+These have middle page numbers of 61, 53, and 29 respectively. Adding these page numbers together gives `143`.
+
+Of course, you'll need to be careful: the actual list of page ordering rules is bigger and more complicated than the above example.
+
+Determine which updates are already in the correct order. What do you get if you add up the middle page number from those correctly-ordered updates?
+
+## Part 2
+
+While the Elves get to work printing the correctly-ordered updates, you have a little time to fix the rest of them.
+
+For each of the incorrectly-ordered updates, use the page ordering rules to put the page numbers in the right order. For the above example, here are the three incorrectly-ordered updates and their correct orderings:
+
+```txt
+75,97,47,61,53 becomes 97,75,47,61,53.
+61,13,29 becomes 61,29,13.
+97,13,75,29,47 becomes 97,75,47,29,13.
+```
+
+After taking only the incorrectly-ordered updates and ordering them correctly, their middle page numbers are 47, 29, and 47. Adding these together produces `123`.
+
+Find the updates which are not in the correct order. What do you get if you add up the middle page numbers after correctly ordering just those updates?

lib/advent_code2024/solutions/day05/day5.ex

@@ -0,0 +1,109 @@
+defmodule AdventCode2024.Solutions.Day05 do
+  @moduledoc """
+  Day 5: Solution for Advent of Code 2024
+  """
+
+  @behaviour AdventCode2024.Solution
+
+  @impl true
+  def solve(""), do: {:error, :no_input}
+
+  def solve(path \\ "priv/inputs/day05/input.txt") do
+    case File.read(path) do
+      {:ok, content} -> solve_content(content)
+      {:error, :enoent} -> {:error, :enoent}
+      _ -> {:error, :no_input}
+    end
+  end
+
+  def solve_content(""), do: {:error, :no_input}
+
+  def solve_content(content) do
+    {rules, updates} = parse_input(content)
+    valid_updates = Enum.filter(updates, &is_valid_update?(&1, rules))
+    sum = valid_updates |> Enum.map(&get_middle_number/1) |> Enum.sum()
+    {:ok, sum}
+  end
+
+  @impl true
+  def solve_part2(""), do: {:error, :no_input}
+
+  def solve_part2(path \\ "priv/inputs/day05/input.txt") do
+    case File.read(path) do
+      {:ok, content} -> solve_part2_content(content)
+      {:error, :enoent} -> {:error, :enoent}
+      _ -> {:error, :no_input}
+    end
+  end
+
+  def solve_part2_content(""), do: {:error, :no_input}
+
+  def solve_part2_content(content) do
+    {rules, updates} = parse_input(content)
+    invalid_updates = Enum.reject(updates, &is_valid_update?(&1, rules))
+
+    sum =
+      invalid_updates
+      |> Enum.map(&order_update(&1, rules))
+      |> Enum.map(&get_middle_number/1)
+      |> Enum.sum()
+
+    {:ok, sum}
+  end
+
+  defp parse_input(content) do
+    [rules_str, updates_str] = String.split(content, "\n\n", trim: true)
+    rules = parse_rules(rules_str)
+    updates = parse_updates(updates_str)
+    {rules, updates}
+  end
+
+  defp parse_rules(rules_str) do
+    rules_str
+    |> 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_str) do
+    updates_str
+    |> String.split("\n", trim: true)
+    |> Enum.map(fn line ->
+      line
+      |> String.split(",")
+      |> Enum.map(&String.to_integer/1)
+    end)
+  end
+
+  defp is_valid_update?(update, rules) do
+    update
+    |> Enum.chunk_every(2, 1, :discard)
+    |> Enum.all?(fn [a, b] -> is_valid_order?(a, b, rules) end)
+  end
+
+  defp is_valid_order?(a, b, rules) do
+    not Enum.any?(rules, fn {x, y} -> x == b and y == a end)
+  end
+
+  defp get_middle_number(list) do
+    middle_index = div(length(list), 2)
+    Enum.at(list, middle_index)
+  end
+
+  defp order_update(update, rules) do
+    update
+    |> Enum.sort(fn a, b ->
+      case {should_come_before?(a, b, rules), should_come_before?(b, a, rules)} do
+        {true, false} -> true
+        {false, true} -> false
+        _ -> a > b
+      end
+    end)
+  end
+
+  defp should_come_before?(a, b, rules) do
+    Enum.any?(rules, fn {x, y} -> x == a and y == b end)
+  end
+end

test/advent_code2024/solutions/day03/day3_test.exs

@@ -8,7 +8,7 @@ defmodule AdventCode2024.Solutions.Day03Test do
     end
 
     test "returns error for invalid file" do
-      assert Day03.solve("nonexistent.txt") == {:error, :enoent}
+      assert Day03.solve("priv/nonexistent.txt") == {:error, :enoent}
     end
 
     test "handles single valid multiplication" do
@@ -48,7 +48,7 @@ defmodule AdventCode2024.Solutions.Day03Test do
     end
 
     test "returns error for invalid file" do
-      assert Day03.solve_part2("nonexistent.txt") == {:error, :enoent}
+      assert Day03.solve_part2("priv/nonexistent.txt") == {:error, :enoent}
     end
 
     test "handles single multiplication with do/don't controls" do

test/advent_code2024/solutions/day05/day5_test.exs

@@ -0,0 +1,184 @@
+defmodule AdventCode2024.Solutions.Day05Test do
+  use ExUnit.Case
+  alias AdventCode2024.Solutions.Day05
+
+  @example_input """
+  47|53
+  97|13
+  97|61
+  97|47
+  75|29
+  61|13
+  75|53
+  29|13
+  97|29
+  53|29
+  61|53
+  97|53
+  61|29
+  47|13
+  75|47
+  97|75
+  47|61
+  75|61
+  47|29
+  75|13
+  53|13
+
+  75,47,61,53,29
+  97,61,53,29,13
+  75,29,13
+  75,97,47,61,53
+  61,13,29
+  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", %{test_file: path} do
+      assert {:ok, 143} = Day05.solve(path)
+    end
+
+    test "returns error for empty input" do
+      assert Day05.solve("") == {:error, :no_input}
+    end
+
+    test "returns error for invalid file" do
+      assert Day05.solve("priv/nonexistent.txt") == {:error, :enoent}
+    end
+
+    test "validates first update is in correct order" do
+      input = """
+      75|47
+      75|61
+      75|53
+      75|29
+      47|61
+      47|53
+      47|29
+      61|53
+      61|29
+      53|29
+
+      75,47,61,53,29
+      """
+      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
+      input = """
+      97|13
+      97|61
+      97|53
+      97|29
+      61|13
+      61|53
+      61|29
+      53|29
+      29|13
+
+      97,61,53,29,13
+      """
+      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
+      input = """
+      97|75
+
+      75,97,47,61,53
+      """
+      path = "test/fixtures/day05/invalid_update.txt"
+      :ok = File.write(path, input)
+      assert {:ok, 0} = Day05.solve(path)
+      File.rm!(path)
+    end
+  end
+
+  describe "solve_part2/1" do
+    test "correctly orders invalid updates and sums middle pages", %{test_file: path} do
+      assert {:ok, 123} = Day05.solve_part2(path)
+    end
+
+    test "correctly orders first invalid update" do
+      input = """
+      75|47
+      75|29
+      47|29
+
+      75,47,29
+      """
+      path = "test/fixtures/day05/part2_first_update.txt"
+      :ok = File.write(path, input)
+      assert {:ok, 47} = Day05.solve_part2(path)
+      File.rm!(path)
+    end
+
+    test "correctly orders second invalid update" do
+      input = """
+      97|13
+      97|29
+      29|13
+
+      97,29,13
+      """
+      path = "test/fixtures/day05/part2_second_update.txt"
+      :ok = File.write(path, input)
+      assert {:ok, 29} = Day05.solve_part2(path)
+      File.rm!(path)
+    end
+
+    test "correctly orders third invalid update" do
+      input = """
+      97|75
+      97|47
+      75|47
+
+      97,75,47
+      """
+      path = "test/fixtures/day05/part2_third_update.txt"
+      :ok = File.write(path, input)
+      assert {:ok, 47} = Day05.solve_part2(path)
+      File.rm!(path)
+    end
+
+    test "ignores already correctly ordered updates" do
+      input = """
+      97|13
+      97|61
+      97|53
+      97|29
+      61|13
+      61|53
+      61|29
+      53|29
+      29|13
+
+      97,61,53,29,13
+      61,53,29,13
+      """
+      path = "test/fixtures/day05/part2_ignore_valid.txt"
+      :ok = File.write(path, input)
+      assert {:ok, 0} = Day05.solve_part2(path)
+      File.rm!(path)
+    end
+  end
+end

test/fixtures/day05/part2_first_update.txt

@@ -0,0 +1,5 @@
+75|47
+75|29
+47|29
+
+75,47,29

test/fixtures/day05/part2_second_update.txt

@@ -0,0 +1,5 @@
+97|13
+97|29
+29|13
+
+97,29,13

test/fixtures/day05/part2_third_update.txt

@@ -0,0 +1,5 @@
+97|75
+97|47
+75|47
+
+97,75,47