Hey Wissal, 4 years later, here is your answer: because we need to add the last empty character ('\0') so that it doesn't stray, cause overflow and keep overwriting with anything

both Alterra and TylerBlue are correct

a string "Hello" is actually "Hello!\0" even though that character is not visible

When none of cases match the value stored in str[i], the default is executed instead. So in this code when str[i] is not a vowel, by default it is added to *ans.

Thanks, this was helpful eventhough I'm a year late.

Thank you very much for the detailed answer.

Thanks!

Can someome please explain me why cant I do the assignment like this : ans[i] = str[i]; ?
Thanx

Clever use of qsort. I asked myself how to sort the ints like this with a single compare function. Thank you for the example. Maybe returning *a -*b or *b - *a could produce some overflows.

nah, I think it's to give extra space in case of memory overflow

This is absolutely NOT "best practice", nor is it clever, as it's modifying a const string it will typically crash.