Originally Posted by zemzela
Could you fix code, it is really important for me. thank you for your time
It's pretty easy, where are you stuck?
Have you figured out how to do it on paper? Cos if you can't do it yourself, then there's no way you'll be able to program a computer to be able to do it.
BTW to the other poster, strcat won't do the trick; the task is to return the *union* of the strings. Think back to set theory. So the union of "123" and "345" is "12345", not "123345" which would be the strcat result.