How to calculate maximum subarray in non_circular part

#1

I am not able to figure out why we are inverting the signs of every element in the and applying kadane’s algorithm to get circular sum?

#2

wrapping exists in elements that will produce maximum subarray sum.
we need to change wrapping-> non wrapping
this can be done by
find out the sum of non contributing elements and subtract this sum from the total sum. To find out the sum of non contributing, invert sign of each element and then run Kadane’s algorithm.
Our array is like a ring and we have to eliminate the maximum continuous negative that implies maximum continuous positive in the inverted arrays