its not readable, short code != the best code.

Given a sequence of integers of length n, print the number of prefix permutations within it.

I don't think it should print the result. This should be changed.

The only performance tests are fixed, and they can be easily hardcoded allowing non-optimal solutions to pass.

How is this not at top?

Added random tests. Guess work solutions killed.

where is the solution?

I think must be test case like [-5,-3,-2,-4,-1] equal 3

Approved

Added a few fixed tests that will catch them.

You know, you can always add if(arr.length < x) in your printing code ;-)

Fixed

Typo in Java Sample test - wrong number params to prefix

assertEquals(PrefixPermutation.prefix(3, new int[]{2, 1, 3, 5, 4}));

Please, add details on the assumptions about the input array such as it containing only positive integers, without repetition, or add some tests.

Also precise input array could be large.

I agree, some solutions return 1 for [2, 2, 2]...

Thank you for the comment. I have considered that.