346. Moving Average from Data Stream 🔒

Description

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.

Solutions

Solution 1

Python3JavaC++Go

class MovingAverage:
    def __init__(self, size: int):
        self.arr = [0] * size
        self.s = 0
        self.cnt = 0

    def next(self, val: int) -> float:
        idx = self.cnt % len(self.arr)
        self.s += val - self.arr[idx]
        self.arr[idx] = val
        self.cnt += 1
        return self.s / min(self.cnt, len(self.arr))


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

class MovingAverage {
    private int[] arr;
    private int s;
    private int cnt;

    public MovingAverage(int size) {
        arr = new int[size];
    }

    public double next(int val) {
        int idx = cnt % arr.length;
        s += val - arr[idx];
        arr[idx] = val;
        ++cnt;
        return s * 1.0 / Math.min(cnt, arr.length);
    }
}

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

class MovingAverage {
public:
    MovingAverage(int size) {
        arr.resize(size);
    }

    double next(int val) {
        int idx = cnt % arr.size();
        s += val - arr[idx];
        arr[idx] = val;
        ++cnt;
        return (double) s / min(cnt, (int) arr.size());
    }

private:
    vector<int> arr;
    int cnt = 0;
    int s = 0;
};

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

type MovingAverage struct {
    arr []int
    cnt int
    s   int
}

func Constructor(size int) MovingAverage {
    arr := make([]int, size)
    return MovingAverage{arr, 0, 0}
}

func (this *MovingAverage) Next(val int) float64 {
    idx := this.cnt % len(this.arr)
    this.s += val - this.arr[idx]
    this.arr[idx] = val
    this.cnt++
    return float64(this.s) / float64(min(this.cnt, len(this.arr)))
}

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

Solution 2

Python3JavaC++Go

class MovingAverage:
    def __init__(self, size: int):
        self.n = size
        self.s = 0
        self.q = deque()

    def next(self, val: int) -> float:
        if len(self.q) ==