[leetcode]346. Moving Average from Data Stream滑动窗口平均值

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

题意：

给定固定长度的滑动窗口，更新滑动窗口中所有数的平均值。

思路：

这种先进先出的特性很适合用queue

若当前queue的size大于sliding window的长度

则从queue中remove一个元素

注意：

全局变量用下划线_size, _sum是个好的coding style

代码：

class MovingAverage {
    Queue<Integer> _queue = new LinkedList<>();
    int _size;
    double _sum;

    /** Initialize your data structure here. */
    public MovingAverage(int size) {
        _size = size;
        _sum = 0.0;
    }
    
    public double next(int val) {
        _queue.add(val);
        _sum = _sum + val;
        if(_queue.size() > _size ){
            _sum = _sum - _queue.remove();
        }
        return _sum/_queue.size();
    }
}

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