[LeetCode] 346. Moving Average from Data Stream

[grandyang]

 

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

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

 

这道题定义了一个MovingAverage类，里面可以存固定个数字，然后我们每次读入一个数字，如果加上这个数字后总个数大于限制的个数，那么我们移除最早进入的数字，然后返回更新后的平均数，这种先进先出的特性最适合使用队列queue来做，而且我们还需要一个double型的变量sum来记录当前所有数字之和，这样有新数字进入后，如果没有超出限制个数，则sum加上这个数字，如果超出了，那么sum先减去最早的数字，再加上这个数字，然后返回sum除以queue的个数即可：

 

class MovingAverage {
public:
    MovingAverage(int size) {
        this->size = size;
        sum = 0;
    }
    
    double next(int val) {
        if (q.size() >= size) {
            sum -= q.front(); q.pop();
        }
        q.push(val);
        sum += val;
        return sum / q.size();
    }
    
private:
    queue<int> q;
    int size;
    double sum;
};

 

类似题目：

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

 

LeetCode All in One 题目讲解汇总(持续更新中...)

[pengxu7]

you can simply use a vector which wraps when there are more than "size" of elements, much more cache friendly.