# 0346. Moving Average from Data Stream

<https://leetcode.com/problems/moving-average-from-data-stream>

## Description

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

Implement the `MovingAverage` class:

* `MovingAverage(int size)` Initializes the object with the size of the window `size`.
* `double next(int val)` Returns the moving average of the last `size` values of the stream.

**Example 1:**

```
**Input**
["MovingAverage", "next", "next", "next", "next"]
[[3], [1], [10], [3], [5]]
**Output**
[null, 1.0, 5.5, 4.66667, 6.0]
**Explanation**
MovingAverage movingAverage = new MovingAverage(3);
movingAverage.next(1); // return 1.0 = 1 / 1
movingAverage.next(10); // return 5.5 = (1 + 10) / 2
movingAverage.next(3); // return 4.66667 = (1 + 10 + 3) / 3
movingAverage.next(5); // return 6.0 = (10 + 3 + 5) / 3
```

**Constraints:**

* `1 <= size <= 1000`
* `-105 <= val <= 105`
* At most `104` calls will be made to `next`.

## ac

```java
class MovingAverage {
    private int size;
    private int sum;
    private Queue<Integer> q;

    /** Initialize your data structure here. */
    public MovingAverage(int size) {
        this.size = size;
        sum = 0;
        q = new LinkedList<>();
    }

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

        return sum * 1.0 / q.size();
    }
}

/**
 * Your MovingAverage object will be instantiated and called as such:
 * MovingAverage obj = new MovingAverage(size);
 * double param_1 = obj.next(val);
 */
```