346

346. Moving Average from Data Stream (Easy)

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.

Companies: Facebook, Spotify, Google, Amazon, Apple

Related Topics:
Array, Design, Queue, Data Stream

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Solution 1.

// OJ: https://leetcode.com/problems/moving-average-from-data-stream/
// Author: github.com/lzl124631x
// Time:
//     MovingAverage: O(1)
//     next: O(1)
// Space: O(S)
class MovingAverage {
private:
    queue<int> q;
    int size, sum = 0;
public:
    MovingAverage(int size) : size(size) { }
    double next(int val) {
        q.push(val);
        sum += val;
        if (q.size() > size) {
            sum -= q.front();
            q.pop();
        }
        return (double)sum / q.size();
    }
};