Watch this video by Errichto. It will give you insights into stress-testing.

Check out AC submissions to the problem — you can see others' submissions and apply filters as well. Pair one with your submission and write a suitable generator (with small test-cases) and you should be able to find some test-case where your code differs in output.

Note that you do not need to have a Linux system for this, you can actually just convert both, your code, and the AC one, into functions and pass them the inputs (while not changing them inside the functions), and compare the outputs. As for generators, you can use rand/srand as shown in the video (or even some exhaustive generator covering all test-cases with n <= 5 for example). Hope this helps!