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
tien0903:
20181223 15:58:33
why others is AC with int althought it has already big number but this one have 2 use long in c++


yaseenmollik:
20181210 23:16:10
Used merge sort..Be careful to use long type instead of integer for count variable. Got wrong answer just for this mistake.. 

manuparmar35:
20181114 19:33:58
Fenwick Tree :: AC in one go :) 

r15habhgup11:
20181030 11:05:02
solved using fenwick tree. ac in one go :) 

eng_hardik:
20181028 20:15:46
Use long in JAVA for storing the inversioncount to avoid WA 

salman3007:
20181010 16:22:44
beautiful use of merge_sort 

kishan75:
20181010 07:52:45
can anyone tell me constraints of test case T 

yash0530:
20180813 12:57:57
Use long to count inversions i got WA for using int in C++ 

divyansh_soni:
20180812 15:42:54
AC in first go by Using BIT.


ayusofayush:
20180809 21:45:22
an application of merge sort.... ;) 
Added by:  Paranoid Android 
Date:  20100306 
Time limit:  3.599s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: PERL6 