시간 제한 | 메모리 제한 | 제출 | 정답 | 맞힌 사람 | 정답 비율 |
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1 초 | 256 MB | 4648 | 2117 | 1531 | 45.417% |
A permutation of integers from 1 to n is a sequence a1, a2, ..., an, such that each integer from 1 to n is appeared in the sequence exactly once.
Two integers in а permutation form an inversion, when the bigger one is before the smaller one.
As an example, in the permutation 4 2 7 1 5 6 3, there are 10 inversions in total. They are the following pairs: 4–2, 4–1, 4–3, 2–1, 7–1, 7–5, 7–6, 7–3, 5–3, 6–3.
Write program invcnt that computes the number of the inversions in a given permutation.
The value for the number n is written on the first line of the standard input. The permutation is written on the second line: n numbers, delimited by spaces.
Write the count of inversions on the standard output.
7 4 2 7 1 5 6 3
10