Moving Average from Data Stream LT346

Given a stream of integers and a window size, calculate the moving average of all integers in the sliding window.

For example,

MovingAverage m = new MovingAverage(3);
m.next(1) = 1
m.next(10) = (1 + 10) / 2
m.next(3) = (1 + 10 + 3) / 3
m.next(5) = (10 + 3 + 5) / 3

 

Idea 1. Sliding window, we need to store elements and poll out the first element when reaching the window size, it looks like queue strucutre fits our needs, it's first-in-first-out.

Time complexity: O(n)

Space complexity: O(k) k is the size of the sliding window

 public class MovingAverage {
     private Queue<Integer> queue;
     private int capacity;
     private double sum;
     /** Initialize your data structure here. */
     public MovingAverage(int size) {
         queue = new ArrayDeque<>();
         capacity = size;
         sum = 0;
     }
 
     public double next(int val) {
         if(queue.size() == capacity) {
             sum -= queue.poll();
         }
         queue.offer(val);
         sum += val;
         return sum/queue.size();
     }
 
     public static void main(String[] args) {
         int[] nums = {1, 10, 3, 5};
         MovingAverage movingAverage = new MovingAverage(3);
         for(int num: nums) {
             System.out.println(movingAverage.next(num));
         }
     }
 }

python:

 import queue
 
 class MovingAverage:
     def __init__(self, capacity):
         self.capacity = capacity
         self.sum = 0
         self.window = queue.Queue(capacity)
 
     def next(self, num):
         if self.window.full():
             self.sum -= self.window.get()
 
         self.sum += num
         self.window.put(num)
         return self.sum/self.window.qsize()
 
 def test():
         test_data = [1, 10, 3, 5]
         test_subject = MovingAverage(3)
         for num in test_data:
             print (test_subject.next(num))
 
 if __name__ == '__main__':
         test()