Day 2 Part 1

day2/day2part1.exs

@@ -0,0 +1,21 @@
+defmodule Day2Part1 do
+  def run do
+    regex = ~r/\A(\d+)-(\d+) (\w): (\w+)\z/
+
+    File.read!("input")
+    |> String.trim()
+    |> String.split("\n")
+    |> Enum.map(&Regex.run(regex, &1, capture: :all_but_first))
+    |> Enum.map(fn [least, most, char, password] ->
+      {String.to_integer(least), String.to_integer(most), char, password}
+    end)
+    |> Enum.filter(fn {least, most, char, password} ->
+      count = Enum.count(String.graphemes(password), &(&1 == char))
+      least <= count && count <= most
+    end)
+    |> Enum.count()
+    |> IO.puts()
+  end
+end
+
+Day2Part1.run()