how can i wrote a prog that dont allows to write in massive same ellements, for example X[1]=10,x[2]=10 ERROR write x[2] again

Question

c++

Answer 1

Provide a trial then I or someone else will help.

Answer 2

Everytime you enter a value, if the value has already appeared, stop or print sth or whatever, but if it has not, add it to the appeared values, and provide a way to enter another number.

Answer 3

https://code.sololearn.com/cMvzE1i27d2B/?ref=app

Answer 4

i understand that, but how can i write if the value already appear?