class MovingAverage
    attr_accessor :size, :queue
=begin
    Initialize your data structure here.
    :type size: Integer
=end
    def initialize(size)
        @size = size
        @queue = []
        @sum = 0.0
    end


=begin
    :type val: Integer
    :rtype: Float
=end
    def next(val)
        if queue.size < size
            queue.unshift(val)
            # strange that attr_accessor :sum
            # does not work
            # repl kept complaining about undefined method +
            # on nil class for sum += val
            # even though p sum.class says it is a Fixnum
            @sum += val
        else
            @sum -= queue.unshift(val).pop
            @sum += val
        end

        @sum / queue.size
    end
end

# Your MovingAverage object will be instantiated and called as such:
# obj = MovingAverage.new(size)
# param_1 = obj.next(val)

obj = MovingAverage.new(3)
obj.next(1)
obj.next(3)