Moving Average from Data Stream

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

分析：

利用Queue先进先出的特点即可。

 public class MovingAverage {
     Queue<Integer> q;
     double sum = ;
     int size;

     /** Initialize your data structure here. */
     public MovingAverage(int s) {
         q = new LinkedList();
         size = s;
     }

     public double next(int val) {
         if (q.size() == size) {
             sum = sum - q.poll();
         }
         q.offer(val);
         sum += val;
         return sum / q.size();
     }
 }