Discussion on: Advent of Code 2020 Solution Megathread - Day 15: Rambunctious Recitation

input = [1,17,0,10,18,11,6]

spoken_numbers = {}
current_number = []

# n = 2020 # Part 1
n = 30000000 
n.times do |i|
  if i < input.size
    current_number = input[i]
  else
    last_number_spoken = current_number
    if spoken_numbers[last_number_spoken] != nil
      last_spoken = spoken_numbers[last_number_spoken].last
      if spoken_numbers[last_number_spoken].size == 1
        current_number = 0
      else
        last_spoken_before_that = spoken_numbers[last_number_spoken][-2]
        current_number = last_spoken - last_spoken_before_that
      end
    end
  end

  spoken_numbers[current_number] ||= []
  spoken_numbers[current_number] << i
end

p current_number