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346. Moving Average from Data Stream

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.

Solution:

class MovingAverage {
    Queue<Integer> queue; 
    int size;
    int curSize;
    int curSum;

    public MovingAverage(int size) {
        queue = new ArrayDeque<>();
        this.size = size;
        curSize = 0;
        curSum = 0;
    }

    public double next(int val) {
        if (curSize < size){
            queue.offer(val);
            curSize++;
            curSum = curSum + val;
            return (double) curSum/curSize; 
        }else {
            queue.offer(val);
            int delete = queue.poll();
            curSum = curSum - delete + val;
            return (double) curSum/curSize;
        }


    }
}

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