Counting inversions

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[@ginobean737]

Excellent explanation! This is the BEST explanation of how to count inversions using a merge sort type algorithm that I have found!

[@mishkamn]

Very good straight to the point and clear

[@shahkushal1495]

If courses are bollywood, NTPEL is the Irfan Khan of it.

[@dejavukun]

Thanks a lot sir!

[@AbhishekChaturvedi7]

superb explanation

[@0anant0]

Very nice explanation. Leetcode 493 is based on this.

[@pranavyeleti3499]

sir countR,R should be mergesortcount(A,mid+1,right).i have a dought.correct me if i am wrong

[@cowboymc8230]

What I don't understand is the part : sort and count inversions in L and R. I mean since you sort L and R already, the count of inversions in either L or R would be 0, isn't it?

[@0anant0]

Those recursions occur during the "merge" portion of the L and R halves. The very act of sorting L and R involves 'merge'
e.g.
cInv += mergeSort(lo to mid)