Moving Average from Data Stream

最新推荐文章于 2024-03-28 11:40:37 发布

sjphiChina

最新推荐文章于 2024-03-28 11:40:37 发布

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本文介绍了一种使用队列实现滑动窗口平均值计算的方法，并通过对比两种不同实现方式（队列与列表）讨论了其优缺点。文章还涉及了整型到浮点型的转换细节及逻辑错误排查。

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07/18/2016更新

改为queue来做，最初的做法太2了。

public class MovingAverage {
    Queue<Integer> list;
    int size = 0;
    int sum = 0;

    /** Initialize your data structure here. */
    public MovingAverage(int size) {
        list = new LinkedList<>();
        this.size = size;
    }
    
    public double next(int val) {
        double result = 0.0;
        if (list.size() < size) {
            sum = sum + val;
            list.offer(val);
            result = (double)sum / list.size();
        } else {
            int deletedNum = list.poll();
            sum = sum - deletedNum;
            sum = sum + val;
            result = (double)sum / size;
            list.offer(val);
        }
        return result;
    }
}

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

一道设计题，有3点

1. 一开始，自己用的是queue来做，但是发现，若想每次peek下一个值，都得先poll，这才发现当中问题，改成了list来做，可以做到get(index)，所以用queue和用queue的思想来解决问题是完全不同的做法。

2. 数值转换，如何从int转为double，看当中的错误

3. 逻辑的bug，致命

public class MovingAverage {
    List<Integer> list;
    int size = 0;
    int index = 0;

    /** Initialize your data structure here. */
    public MovingAverage(int size) {
        list = new ArrayList<>();
        this.size = size;
    }
    
    public double next(int val) {
        int sum = 0;
        double result = 0.0;
        list.add(val);
        if (list.size() < size) {
            for (int i = 0; i < list.size(); i++) {
                sum = sum + list.get(i);
            }
            //result = sum / list.size();
            result = (double)sum / list.size();
        } else {
            //for (int i = index; i < size; i++) {
            for (int i = index; i < index + size; i++) {
                sum = sum + list.get(i);
            }
            //result = sum / size;
            result = (double)sum / size;
            index++;
        }
        return result;
    }
}

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