day 4 part 2

lib/advent_of_code/day_04.ex

@@ -3,6 +3,7 @@ defmodule AdventOfCode.Day04 do
     Advent.Code4_1.execute(inp)
   end
 
-  def part2(_args) do
+  def part2(inp) do
+    Advent.Code4_2.execute(inp)
   end
 end

lib/code/day4_1.ex

@@ -19,6 +19,5 @@ defmodule Advent.Code4_1 do
     |> Enum.map(fn el -> length(MapSet.to_list(el)) end)
     |> Enum.filter(fn el -> el != 0 end)
     |> Enum.reduce(0, fn el, acc -> (acc + :math.pow(2, el - 1)) |> round end)
-    |> dbg()
   end
 end

lib/code/day4_2.ex

@@ -0,0 +1,34 @@
+defmodule Advent.Code4_2 do
+  def find_winning_cards_count([], _current), do: 0
+  def find_winning_cards_count(_list, nil), do: 0
+
+  def find_winning_cards_count(list, curr_el) do
+    Enum.slice(list, (curr_el[:id] + 1)..(curr_el[:id] + curr_el[:wins]))
+    |> Enum.reduce(1, fn el, ac -> ac + find_winning_cards_count(list, el) end)
+  end
+
+  def execute(inp) do
+    parsed =
+      inp
+      |> Enum.map(fn el ->
+        [_, data] = String.split(el, ": ", trim: true)
+        data
+      end)
+      |> Enum.map(fn el -> String.split(el, " | ", trim: true) end)
+      |> Enum.map(fn sublist ->
+        Enum.map(sublist, fn e -> String.split(e, " ", trim: true) end)
+      end)
+      |> Enum.map(fn [el, mn] -> %{winning: el, my: mn} end)
+      |> Enum.map(fn row ->
+        w = MapSet.new(row[:winning])
+        m = MapSet.new(row[:my])
+
+        MapSet.intersection(w, m)
+      end)
+      |> Enum.with_index()
+      |> Enum.map(fn {el, idx} -> %{id: idx, wins: MapSet.size(el)} end)
+
+    parsed
+    |> Enum.reduce(0, fn el, acc -> acc + find_winning_cards_count(parsed, el) end)
+  end
+end

test/advent_of_code/day_03_test.exs

@@ -3,7 +3,7 @@ defmodule AdventOfCode.Day03Test do
 
   import AdventOfCode.Day03
 
-  defp test_input1,
+  defp test_input,
     do: """
     467..114..
     ...*......
@@ -18,29 +18,15 @@ defmodule AdventOfCode.Day03Test do
     """
 
   test "part1" do
-    input = test_input1()
+    input = test_input()
     result = part1(input)
 
     assert result == 4361
   end
 
-  defp test_input2,
-    do: """
-    467..114..
-    ...*......
-    ..35..633.
-    ......#...
-    617*......
-    .....+.58.
-    ..592.....
-    ......755.
-    ...$.*....
-    .664.598..
-    """
-
   @tag :skip
   test "part2" do
-    input = test_input2()
+    input = test_input()
     result = part2(input)
 
     assert result == 467_835

test/advent_of_code/day_04_test.exs

@@ -3,7 +3,7 @@ defmodule AdventOfCode.Day04Test do
 
   import AdventOfCode.Day04
 
-  def test_input1(),
+  def test_input(),
     do: """
     Card 1: 41 48 83 86 17 | 83 86  6 31 17  9 48 53
     Card 2: 13 32 20 16 61 | 61 30 68 82 17 32 24 19
@@ -14,17 +14,16 @@ defmodule AdventOfCode.Day04Test do
     """
 
   test "part1" do
-    input = test_input1()
+    input = test_input()
     result = part1(My.Utils.split_file(input, "\n"))
 
     assert result == 13
   end
 
-  @tag :skip
   test "part2" do
-    input = nil
-    result = part2(input)
+    input = test_input()
+    result = part2(My.Utils.split_file(input, "\n"))
 
-    assert result
+    assert result == 30
   end
 end