day15.rb

class Computer
 
  def initialize (filename)
    @data = IO.read(filename).lines.map(&:chomp)
    @record = {}
    @turn = 1
    @previous = {
      'exotic' => true,
      'num' => 0
    }
  end

  def simulate
    start = @data[0].split(",").map { |num| num.to_i}
    start.each do |num|
      @record[num] = {
        'recent' => @turn,
        'earlier' => @turn
      }
      @previous = {'exotic' => true, 'num' => num}
      @turn +=1 
    end
    while @turn < 30000001 do

      if @turn % 15000 === 0
        File.open("./15.log.txt", "a") { |f| f.write "Computed 15000 turns\n\n" }
      end
          if @previous['exotic']
            if @record[0]
              @record[0]['earlier'] = @record[0]['recent']
              @record[0]['recent'] = @turn
              @previous = {'exotic' => false, 'num' => 0}
            else
               @record[0]= {
                'recent' => @turn,
                'earlier' => @turn
              }
              @previous = {'exotic' => true, 'num' => 0}
            end
          else
              new_num = (@turn - 1) - @record[@previous['num']]['earlier']
              if @record[new_num]
                @record[new_num]['earlier'] = @record[new_num]['recent']
                @record[new_num]['recent'] = @turn
                @previous = {'exotic' => false, 'num' => new_num}
              else
                @record[new_num] = {
                  'recent' => @turn,
                  'earlier' => @turn
                }
                @previous = {'exotic' => true, 'num' => new_num}
              end
            end
          @turn +=1
      end
    return @previous
  end
end

c1 = Computer.new ('15.input.txt')


starting = Time.now
p c1.simulate
ending = Time.now
p "computed in #{(ending - starting).floor} seconds"