day4

Author: akdemironur

04/sample_input

@@ -0,0 +1,6 @@
+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
+Card 3:  1 21 53 59 44 | 69 82 63 72 16 21 14  1
+Card 4: 41 92 73 84 69 | 59 84 76 51 58  5 54 83
+Card 5: 87 83 26 28 32 | 88 30 70 12 93 22 82 36
+Card 6: 31 18 13 56 72 | 74 77 10 23 35 67 36 11

04/sol.exs

@@ -0,0 +1,59 @@
+defmodule Day04 do
+  def read_input(file_path) do
+    case File.read(file_path) do
+      {:ok, content} ->
+        content
+        |> String.split(~r/\n/, trim: true)
+        |> Enum.map(&read_line/1)
+
+      {:error, reason} ->
+        raise "Oh no! #{reason}"
+    end
+  end
+
+  def read_line(str) do
+    [_, b, c] =
+      String.split(str, ~r/:|\|/, trim: true) |> Enum.map(&String.split(&1, " ", trim: true))
+
+    {1, MapSet.new(Enum.map(b, &String.to_integer/1)),
+     MapSet.new(Enum.map(c, &String.to_integer/1))}
+  end
+
+  def partA(file_path) do
+    file_path
+    |> read_input
+    |> Enum.map(&number_of_matches/1)
+    |> Enum.map(&point/1)
+    |> Enum.sum()
+  end
+
+  def partB(file_path) do
+    rem = file_path |> read_input
+
+    add_duplicates(hd(rem), tl(rem), [])
+    |> Enum.map(&elem(&1, 0))
+    |> Enum.sum()
+  end
+
+  def number_of_matches({_, x, y}), do: MapSet.intersection(x, y) |> MapSet.size()
+
+  def point(0), do: 0
+  def point(num_of_matches), do: 2 ** (num_of_matches - 1)
+
+  def add_to_next_N(0, _, l, acc), do: Enum.reverse(acc) ++ l
+  def add_to_next_N(_, _, [], acc), do: Enum.reverse(acc)
+
+  def add_to_next_N(n, val, [{a, b, c} | rest], acc) do
+    add_to_next_N(n - 1, val, rest, [{a + val, b, c} | acc])
+  end
+
+  def add_duplicates(current_card, [], acc), do: Enum.reverse([current_card | acc])
+
+  def add_duplicates({k, x, y}, remaining_cards, acc) do
+    new_rem = add_to_next_N(number_of_matches({k, x, y}), k, remaining_cards, [])
+    add_duplicates(hd(new_rem), tl(new_rem), [{k, x, y} | acc])
+  end
+end
+
+IO.puts(Day04.partA("./input"))
+IO.puts(Day04.partB("./input"))