Add Day 5 alternative parser implementation

day5/README

@@ -48,13 +48,7 @@ I quite enjoyed this one, maybe because it's a Saturday and I wasn't burnt out f
 After reading the Elixir Forum thread: https://elixirforum.com/t/advent-of-code-2020-day-5/35997/
 
 I really had to have a go at just parsing the boarding pass directly into an integer. I said I wouldn't
-commit code to my solutions after reading forums, so I'll add it here instead :-) It converts each
-character to a bit on the fly, and interprets the result as a 10-bit integer. 🦾
+commit code to my solutions after reading forums, but as long as it's clearly labelled, I think it's fine.
 
-  def char_to_bit(c) when c in 'FL', do: <<0::1>>
-  def char_to_bit(c) when c in 'BR', do: <<1::1>>
+It converts each character to a bit on the fly, and interprets the result as a 10-bit integer. 🦾
 
-  def seat_id_bitstring(boarding_pass \\ "FBFBBFFRLR") do
-    <<id::integer-10>> = for <<char <- boarding_pass>>, into: <<>>, do: char_to_bit(char)
-    id
-  end

day5/day5part1.exs

@@ -27,6 +27,18 @@ defmodule Day5Part1 do
 
     row * 8 + col
   end
+
+  # ALTERNATIVE PARSER ADDED AFTER READING OTHER SUBMISSIONS
+  # The boarding pass is actually just a binary number, so we can parse it as such directly.
+  # (The *8 above is eqivalent to the 3-bit shift to the left)
+  def char_to_bit(c) when c in 'FL', do: <<0::1>>
+  def char_to_bit(c) when c in 'BR', do: <<1::1>>
+
+  def seat_id_bitstring(boarding_pass \\ "FBFBBFFRLR") do
+    boarding_pass = String.trim(boarding_pass)
+    <<id::integer-10>> = for <<char <- boarding_pass>>, into: <<>>, do: char_to_bit(char)
+    id
+  end
 end
 
 Day5Part1.run()

day5/day5part2.exs

@@ -35,6 +35,18 @@ defmodule Day5Part2 do
 
     row * 8 + col
   end
+
+  # ALTERNATIVE PARSER ADDED AFTER READING OTHER SUBMISSIONS
+  # The boarding pass is actually just a binary number, so we can parse it as such directly.
+  # (The *8 above is eqivalent to the 3-bit shift to the left)
+  def char_to_bit(c) when c in 'FL', do: <<0::1>>
+  def char_to_bit(c) when c in 'BR', do: <<1::1>>
+
+  def seat_id_bitstring(boarding_pass \\ "FBFBBFFRLR") do
+    boarding_pass = String.trim(boarding_pass)
+    <<id::integer-10>> = for <<char <- boarding_pass>>, into: <<>>, do: char_to_bit(char)
+    id
+  end
 end
 
 Day5Part2.run()