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
shreeshiv:
20170220 10:13:59
What is WA and AC??


nilabja16180:
20170213 13:47:11
A great BIT problem 

fane_faiz:
20170209 10:21:48
Don't forget to use long long, caused me 2 WA.


sks4903440:
20170207 20:24:44
Don't forget to use long long. 

akash_23:
20170207 18:53:16
did using BIT, easy AC! tag helped me to get the idea :P 

zhanbolat:
20170122 17:32:14
I didn't get relation between graph theory and this problem.


muneebaadil:
20170120 18:15:37
Oh damn you long long! Probably a lesson for me to be conscious with data types from now on.. 

scorpion_ajay:
20170119 11:44:24
best for learners, learning overloaded, spent two days, came out of no hope.


gauravgb21:
20161229 07:59:30
jst modify the mergesort algorithm


aditya930:
20161227 23:53:59
use enhanced merge sort and long long to get AC !! 
Added by:  Paranoid Android 
Date:  20100306 
Time limit:  3.599s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: PERL6 