给定一个整数数据流和一个窗口大小，根据该滑动窗口的大小，计算滑动窗口里所有数字的平均值。
实现 MovingAverage 类：
MovingAverage(int size)用窗口大小size初始化对象。double next(int val)成员函数next每次调用的时候都会往滑动窗口增加一个整数，请计算并返回数据流中最后size个值的移动平均值，即滑动窗口里所有数字的平均值。
示例：
输入：
inputs = ["MovingAverage", "next", "next", "next", "next"]
inputs = [[3], [1], [10], [3], [5]]
输出：
[null, 1.0, 5.5, 4.66667, 6.0]
解释：
MovingAverage movingAverage = new MovingAverage(3);
movingAverage.next(1); // 返回 1.0 = 1 / 1
movingAverage.next(10); // 返回 5.5 = (1 + 10) / 2
movingAverage.next(3); // 返回 4.66667 = (1 + 10 + 3) / 3
movingAverage.next(5); // 返回 6.0 = (10 + 3 + 5) / 3提示：
1 <= size <= 1000-105 <= val <= 105- 最多调用
next方法104次
//leetcode submit region begin(Prohibit modification and deletion)
class MovingAverage {
private long sum;
private int size;
private Queue<Integer> myQ;
/** Initialize your data structure here. */
public MovingAverage(int size) {
this.size = size;
this.sum = 0;
this.myQ = new LinkedList<>();
}
public double next(int val) {
if (myQ.size() == size) {
sum -= myQ.poll();
}
myQ.add(val);
sum += val;
return ((double)sum) / myQ.size();
}
}
/**
* Your MovingAverage object will be instantiated and called as such:
* MovingAverage obj = new MovingAverage(size);
* double param_1 = obj.next(val);
*/
//leetcode submit region end(Prohibit modification and deletion)
