Thursday, June 2, 2016

Leetcode: 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.
For 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

Solution:
Use a Queue serve as a sliding window, and also maintain the current sum inside of the window. 

Code (Java):
public class MovingAverage {
    Queue<Integer> queue;
    int n;
    int sum;
    
    /** Initialize your data structure here. */
    public MovingAverage(int size) {
        queue = new LinkedList<>();
        n = size;
        sum = 0;
    }
    
    public double next(int val) {
        queue.offer(val);
        double result = 0;
        sum += val;
        if (queue.size() <= n) {
            result = (double) sum / queue.size();
        } else {
            int remove = queue.poll();
            sum -= remove;
            result = (double) sum / n;
        }
        
        return result;
    }
}

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

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