原题链接在这里：

题目：

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

题解：

维护一个queue, 当queue的size已经等于size时若是继续加新的val就需要poll值.

Time Complexity: MovingAverage(size) O(1), next(val) O(1).

Space: O(size) 需要维护queue

AC Java:

1 public class MovingAverage { 2      3     private LinkedList
     
       que; 4     private int size; 5     private int sum; 6      7     /** Initialize your data structure here. */ 8     public MovingAverage(int size) { 9         this.que = new LinkedList
      
       ();10         this.size = size;11         this.sum = 0;12     }13     14     public double next(int val) {15         if(que.size() == this.size){16             this.sum -= que.poll();17         }18         que.offer(val);19         sum += val;20         return (double)this.sum/que.size();21     }22 }23 24 /**25  * Your MovingAverage object will be instantiated and called as such:26  * MovingAverage obj = new MovingAverage(size);27  * double param_1 = obj.next(val);28  */