Maximum Average Subarray I

Problem:

Given an array consisting of n integers, find the contiguous subarray of given length k that has the maximum average value. And you need to output the maximum average value.

Example 1:

Input: [1,12,-5,-6,50,3], k = 4
Output: 12.75
Explanation: Maximum average is (12-5-6+50)/4 = 51/4 = 12.75

Note:

1. 1 <= k <= n <= 30,000.
2. Elements of the given array will be in the range [-10,000, 10,000].

Analysis:

Simplified version of Maximum Subarray IV. Keep a window without updating minSum. 

Solution:

class Solution {
    public double findMaxAverage(int[] nums, int k) {
        int slowSum = 0, fastSum = 0, max = 0;
        for (int i = 0; i < k; i++) {
            fastSum += nums[i];
        }
        max = fastSum;
        for (int i = k; i < nums.length; i++) {
            slowSum += nums[i - k];
            fastSum += nums[i];
            max = Math.max(fastSum - slowSum, max);
        }
        
        return max/(double)k;
    }
}