Sliding Window: maxSubarraySum

Given an array of integers and a number, write a function called maxSubarraySum, which finds the maximum sum of a subarray with the length of the number passed to the function.

Note that a subarray must consist of consecutive elements from the original array. In the first example below, [100,200,300] is a subarray of the original array, but [100,300] is not.

 

1. maxSubarraySum([100,200,300,400], 2) // 700
2. maxSubarraySum([1,4,2,10,23,3,1,0,20], 4) // 39
3. maxSubarraySum([-3,4,0,-2,6,-1], 2) // 5
4. maxSubarraySum([3,-2,7,-4,1,-1,4,-2,1],2) // 5
5. maxSubarraySum([2,3], 3) // null