In the rules of this forum is written, that this forum is not for general c questions and only for codeblocks questions. Not reading the forum rules is a reason for a ban, so stahta is (a bit rudely) saying you should read and follow the forum rules and not ask this kind of questions on this forum.
In case of RAND() C command is it possible to avoid double same results like
4 1 1 3 5 in case of randon of 5 numbers generated by rand()
No, because you want to have random numbers....
basically this is also a random sequence:
obligatory XKCD for reference:
https://www.xkcd.com/221/