An inversion in a list of distinct integers (a1, . . . , an) is a pair ai, aj such that i < j and ai > aj . Fnd the value of the biggest difference among inversion pairs. Example: for the sequence [11, 7, 1, 17, 4, 3, 6, 2, 13, 20, 15, 9], the greatest difference among all inversion pairs is 15 coming from the pair (17, 2).

Design a divide and conquer type algorithm in O(nlogn) runtime that uses mergesort and finds the value of the greatest difference between all inversion pairs in a list of distinct integers.

I think you can keep track of the max difference when you try to merge the two arrays in mergesort but i'm having trouble with the pseudocode.