INVCNT  Inversion Count
Let A[0...n  1] be an array of n distinct positive integers. If i < j and A[i] > A[j] then the pair (i, j) is called an inversion of A. Given n and an array A your task is to find the number of inversions of A.
Input
The first line contains t, the number of testcases followed by a blank space. Each of the t tests start with a number n (n <= 200000). Then n + 1 lines follow. In the ith line a number A[i  1] is given (A[i  1] <= 10^7). The (n + 1)th line is a blank space.
Output
For every test output one line giving the number of inversions of A.
Example
Input: 2 3 3 1 2 5 2 3 8 6 1 Output: 2 5
hide comments
carofe82:
20240807 17:00:39
I got AC with golang. As others have said, make sure you use int64 for the result count. 

hs1800002:
20240605 02:22:35
<snip>


pudo1234:
20240325 09:20:56
@onis No you use your brain so I don't think you can solve it


onis:
20240325 09:20:05
guys do I use the amogus method to solve this????? 

pratyushgadge1:
20231013 20:41:33
i agree with @hraj123. don't use int. i used long long and got my solution accepted in the first try after the update; 

orgil0127:
20230627 06:57:03
HELLO world <2


hraj123:
20230610 12:28:50
@new_mutant, it will overflow bcoz of array size not bcoz of array values, as total pair values can have upperbound as (n^2n)/2 where n<=2e5. Last edit: 20230627 19:31:46 

leonardodpv:
20230508 02:10:41
Ojo con el numero de "inversions" que se pueden dar en casos muy grandes y ordenados. Last edit: 20230508 02:11:02 

mddinislam:
20230504 14:06:55
How the first test case answer is 2 ? 

cprakash123:
20230327 18:57:36
solving first time ........... 
Added by:  Paranoid Android 
Date:  20100306 
Time limit:  3.599s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: PERL6 