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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] ≤ 107). 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
Added by: | Paranoid Android |
Date: | 2010-03-06 |
Time limit: | 3.599s |
Source limit: | 50000B |
Memory limit: | 1536MB |
Cluster: | Cube (Intel G860) |
Languages: | All except: PERL6 |
hide comments
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2017-03-15 16:36:06
For Those who are looking for hints. Well Fenwick tree has a property of counting inversions in an array. Did a lot of work improving time complexity.Great problem. You just have to take care of duplicate elements.AC |
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2017-03-09 10:39:55
ha ha long long |
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2017-03-03 16:20:51
too weak tests!!!! I got the AC using a vector and inserting elements in their true positions and asking if there was any element bigger than this before this one was added... it should be TLE but it is AC! Last edit: 2017-03-03 16:22:05 |
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2017-02-20 10:13:59
What is WA and AC?? |
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2017-02-13 13:47:11
A great BIT problem |
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2017-02-09 10:21:48
Don't forget to use long long, caused me 2 WA. |
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2017-02-07 20:24:44
Don't forget to use long long. |
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2017-02-07 18:53:16
did using BIT, easy AC! tag helped me to get the idea :P |
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2017-01-22 17:32:14
I didn't get relation between graph theory and this problem. Can somebody share with #graph,#shortest path solution ? Last edit: 2017-01-22 17:33:06 |
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2017-01-20 18:15:37
Oh damn you long long! Probably a lesson for me to be conscious with data types from now on.. |