Discussion on: Advent of Code 2020 Solution Megathread - Day 5: Binary Boarding

[Derek Wright]

Ruby, Late to the party - catching up!

I see lots of complex solutions when binary data packing/unpacking should be relatively compact and optimized. Hopefully this helps give people some ideas!

# Read a line and parse it w/ convert
def parse(data)
    (convert(data[0..6], 'F', 'B') * 8) +
    convert(data[7..9], 'L', 'R')
end

# Converts data into a binary 0/1 string and then gets the dec value
def convert(data, off_char, on_char)
  data.scan(/[#{off_char}|#{on_char}]/).map { |c| c == off_char ? 0 : 1 }.join('').to_i(2)
end

# Part One
seats = File.readlines('input.txt').map { |s| parse(s) }.sort
p seats.last

# Part Two
parted_seats = seats.slice_when {|i, j| i+1 != j }.to_a
p (parted_seats.first.last..parted_seats.last.first).to_a[1]