### 2D Array Max Subarray Sum

Write a function `maxSubarraySum`

that, given a non-rectangular two-dimensional non-nullable `Int`

array,
returns the sum of the subarray that sums to the largest value.

So given the following array, with each subarray on a separate line:

You would return 7. The passed array will contain no empty subarrays.

One hint for this problem is that you may need both an `Int`

variable to store the max *and* a `Boolean`

variable
to record whether the maximum value has been initialized.
Once you have summed each subarray, check whether either your `Boolean`

value is `false`

*or* the sum is larger than
the largest you've seen so far.
After you check the sum of the first subarray, set your `Boolean`

value to `true`

.
Another approach is to use the counter that you use to proceed through each subarray to determine whether you have
initialized the max value.