2023 day2

lib/2023_day2.exs

@@ -0,0 +1,61 @@
+red_limit = 12
+green_limit = 13
+blue_limit = 14
+
+parse_rounds = fn s ->
+  s
+  |> String.split(";")
+  |> Enum.map(
+    &Enum.map(
+      String.split(&1, ","),
+      fn x ->
+        [_, count, color] = Regex.run(~r/(\d+) (.+)/, String.trim(x))
+        {count, _} = count |> Integer.parse()
+        color = color |> String.to_atom()
+
+        {color, count}
+      end
+    )
+  )
+end
+
+all_games =
+  for line <- IO.stream(),
+      line |> String.trim() |> String.length() > 0,
+      [_, id, rounds] = Regex.run(~r/Game (\d+): (.+)/, line) do
+    {id |> Integer.parse() |> elem(0), parse_rounds.(rounds)}
+  end
+
+part1 = fn games ->
+  games
+  |> Enum.filter(fn {_, games} ->
+    Enum.all?(games, fn game ->
+      game |> Keyword.get(:green, 0) <= green_limit &&
+        game |> Keyword.get(:red, 0) <= red_limit &&
+        game |> Keyword.get(:blue, 0) <= blue_limit
+    end)
+  end)
+  |> Enum.map(&elem(&1, 0))
+  |> Enum.sum()
+end
+
+part2 = fn games ->
+  games
+  |> Enum.map(
+    &(elem(&1, 1)
+      |> Enum.reduce(
+        {0, 0, 0},
+        fn round, {red, green, blue} ->
+          {
+            max(red, Keyword.get(round, :red, 0)),
+            max(green, Keyword.get(round, :green, 0)),
+            max(blue, Keyword.get(round, :blue, 0))
+          }
+        end
+      ))
+  )
+  |> Enum.map(fn {x, y, z} -> x * y * z end)
+  |> Enum.sum()
+end
+
+part2.(all_games) |> IO.puts()