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346. 数据流中的移动平均值

English Version

题目描述

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，计算其所有整数的移动平均值。

实现 MovingAverage 类：

• MovingAverage(int size) 用窗口大小 size 初始化对象。
• double next(int val) 计算并返回数据流中最后 size 个值的移动平均值。

 

示例：

输入：
["MovingAverage", "next", "next", "next", "next"]
[[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

解法

“循环数组”实现。

Python3

class MovingAverage:

    def __init__(self, size: int):
        """
        Initialize your data structure here.
        """
        self.size = size
        self.data = [0] * size
        self.count = 0
        self.s = 0

    def next(self, val: int) -> float:
        idx = self.count % self.size
        old_val = self.data[idx]
        self.data[idx] = val
        self.s += (val - old_val)
        self.count += 1
        return self.s / min(self.size, self.count)


# Your MovingAverage object will be instantiated and called as such:
# obj = MovingAverage(size)
# param_1 = obj.next(val)

Java

class MovingAverage {
    private int size;
    private int[] data;
    private int count;
    private int s;

    /** Initialize your data structure here. */
    public MovingAverage(int size) {
        this.size = size;
        this.data = new int[size];
    }
    
    public double next(int val) {
        int idx = count % size;
        int oldVal = data[idx];
        data[idx] = val;
        s += (val - oldVal);
        ++count;
        return s * 1.0 / Math.min(size, count);
    }
}

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

...