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
sangmai:
20200117 03:14:50
AC in one go using merge sort 

sajalagrawal14:
20191203 13:46:03
Can be solved Using


codefresher:
20191122 22:44:54
Good one....solved using merge sort tree...segment tree??? 

abhishak69:
20191122 21:51:35
my first fenwick tree question :) 

ishancosmos25:
20191110 05:27:54
Used BIT and inversions count to solve the problem.


theviralv:
20191105 10:36:43
we can use ordered set (pb_ds) to solve this.... 

gabadzeluka:
20191103 10:56:10
Solve using Merge sort first, after that solve it with BIT (Binary indexed tree). AC in one go ;) 

mohammadsaad:
20191101 04:44:13
input explanation is garbage , but BIT DESTROY it!! 

scorpy1:
20190913 11:13:23
AC in 3 GO because of long long! 

fardin_abir:
20190909 08:32:00
can anyone please tell me how to solve it using segment tree....?

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