2018-10-18 Moving Average from Data Stream [E]

642. Moving Average from Data Stream
     LC: 346
     Given a stream of integers and a window size, calculate the moving average of all integers in the sliding window.

Example
MovingAverage m = new MovingAverage(3);
m.next(1) = 1 // return 1.00000
m.next(10) = (1 + 10) / 2 // return 5.50000
m.next(3) = (1 + 10 + 3) / 3 // return 4.66667
m.next(5) = (10 + 3 + 5) / 3 // return 6.00000

class MovingAverage:
    """
    @param: size: An integer
    """
    def __init__(self, size):
        # do intialization if necessary
        self.total = 0
        self.cap = size
        self.nums = []

    """
    @param: val: An integer
    @return:  
    """
    def next(self, val):
        # write your code here
        if len(self.nums) == self.cap:
            self.total -= self.nums.pop(0)
        self.nums.append(val)
        self.total += val
        return self.total / len(self.nums)

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

• Time: O(1) for both
• Space: O(size) for the object

Notes:
One key point here is to use a queue to keep track of all nums in window.