screw it do part 1 of 2021 day 3 again, even if it's backwards

2021/day3.exs

@@ -1,24 +1,40 @@
 defmodule Day3 do
+  def part1(input) do
+    gamma_rating = find_rating(input, 0, :most, <<>>)
+    epsillon_rating = find_rating(input, 0, :least, <<>>)
+    gamma_rating * epsillon_rating
+  end
+
+  defp find_rating([value | _], _, _, bits) when bit_size(value) == bit_size(bits) do
+    <<rating::size(bit_size(bits))>> = bits
+    rating
+  end
+
+  defp find_rating(values, bits_seen, mode, acc) do
+    bit = find_common(values, bits_seen, mode)
+    find_rating(values, bits_seen + 1, mode, <<acc::bits-size(bits_seen), bit::1>>)
+  end
+
   def part2(input) do
-    oxygen_generator_rating = find_rating(input, 0, :oxygen_generator)
+    oxygen_generator_rating = find_rating2(input, 0, :most)
-    co2_scrubber_rating = find_rating(input, 0, :co2_scrubber)
+    co2_scrubber_rating = find_rating2(input, 0, :least)
     oxygen_generator_rating * co2_scrubber_rating
   end
 
-  def find_rating([bits], _bits_seen, _mode) do
+  defp find_rating2([bits], _bits_seen, _mode) do
     <<value::size(bit_size(bits))>> = bits
     value
   end
 
-  def find_rating(values, bits_seen, mode) do
+  defp find_rating2(values, bits_seen, mode) do
     bit = find_common(values, bits_seen, mode)
 
     values
     |> filter_by_bit(bits_seen, bit)
-    |> find_rating(bits_seen + 1, mode)
+    |> find_rating2(bits_seen + 1, mode)
   end
 
-  def find_common(values, bits_seen, mode) do
+  defp find_common(values, bits_seen, mode) do
     {zeros, ones} =
       values
       |> Enum.map(fn <<_::size(bits_seen), bit::1, _rest::bits>> -> bit end)
@@ -28,12 +44,12 @@ defmodule Day3 do
       end)
 
     case mode do
-      :oxygen_generator -> if zeros <= ones, do: 1, else: 0
+      :most -> if zeros <= ones, do: 1, else: 0
-      :co2_scrubber -> if zeros <= ones, do: 0, else: 1
+      :least -> if zeros <= ones, do: 0, else: 1
     end
   end
 
-  def filter_by_bit(values, num_prev_bits, bit) do
+  defp filter_by_bit(values, num_prev_bits, bit) do
     Enum.filter(values, &match?(<<_::size(num_prev_bits), ^bit::1, _rest::bits>>, &1))
   end
 
@@ -55,13 +71,18 @@ defmodule Day3 do
   def run do
     case input() do
       :error -> print_usage()
-      input -> run_with_timer(fn -> part2(input) end)
+      input -> run_parts_with_timer(input)
     end
   end
 
-  defp run_with_timer(fun) do
+  defp run_parts_with_timer(input) do
+    run_with_timer(1, fn -> part1(input) end)
+    run_with_timer(2, fn -> part2(input) end)
+  end
+
+  defp run_with_timer(part, fun) do
     {time, result} = :timer.tc(fun)
-    IO.puts("Part 2 (completed in #{format_time(time)}):\n")
+    IO.puts("Part #{part} (completed in #{format_time(time)}):\n")
     IO.puts("#{result}\n")
   end
 
@@ -70,7 +91,7 @@ defmodule Day3 do
   defp format_time(μsec), do: "#{μsec / 1_000_000}s"
 
   defp print_usage do
-    IO.puts("Usage: elixir day3.exs input_filename")
+    IO.puts("Usage: elixir dayREPLACE_ME.exs input_filename")
   end
 end