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
jmdalida11:
20221107 14:44:15
I solved it using a binary tree :) 

osman_goni_:
20220808 17:59:27
Can this problem can be solved using Segment tree ? 

spongecodes:
20220111 20:03:21
why is my solution accepted in CPP 14 but giving WA in C++ ? 

new_mutant:
20220103 15:17:13
you have given that arr[i1]<=10^7 , but it causes int overflow, when i used long long it got submitted, please correct it. Last edit: 20220103 15:17:27 

atishya_20:
20211227 07:23:11
AC in one GO Using ordered set 

mohit_010:
20211113 08:37:16
<snip>


4444:
20211103 13:52:57
@sabkx thanks a lot for the long long int comment 

sabkx:
20211003 07:06:22
EZ AC in second go! use long long instead of int. Merge sort works with 0.11 second 

jdmoyle:
20210819 06:33:52
Fenwick Tree :D, return type long long int 

ss_sri:
20210816 11:15:07
IDK but i am not able to solve it using merge sort, it says SEGMENTATION FAULT.

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