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
abdrakhman:
20170602 09:48:56
AC in one go)))) 

anurag44:
20170525 04:38:39
Core concept of sorting algorithm.. 

thefriction:
20170502 14:53:24
thanks @fane_faiz :)


akt_1998:
20170410 19:42:03
Merge Sort>"ACIN1GO" 

babur:
20170405 20:10:49
Segment Tree+Merge Sort AC in 1 go :) 

the_novice96:
20170405 14:12:46
If BST implementation gets AC, then the test cases are weak because the running time for BST is O(nh), which is O(n^2) in worst case. Basically it should fail if the sequence is sorted. 

amandal799:
20170323 18:42:59
solved using binary search tree..AC in one go 

rohit9934:
20170315 16:36:06
For Those who are looking for hints.


jeelapamy:
20170309 10:39:55
ha ha long long 

anaar_13:
20170303 16:20:51
too weak tests!!!!

Added by:  Paranoid Android 
Date:  20100306 
Time limit:  3.599s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: PERL6 