wip: day 1

2025/day1.ex

@@ -0,0 +1,26 @@
+ops = ["L50", "R50", "R1"]
+
+defmodule Dial do
+  # Initial conditions
+  def rotate(operations), do: rotate(50, operations, 0)
+
+  # When no operations remain, return the number of zeroes
+  def rotate(_, [], zeroes), do: zeroes
+
+  # Compute the new dial position
+  def rotate(index, [head | tail], zeroes) do
+    index = case head do
+      "R" <> number -> index + String.to_integer(number)
+      "L" <> number -> index - String.to_integer(number)
+    end
+
+    case index do
+      0 -> rotate(index, tail, zeroes+1)
+      _ -> rotate(index, tail, zeroes)
+    end
+  end
+end
+
+dial = Dial.rotate(ops)
+
+IO.puts dial