Does Unordered Set Allow Duplicates?

Unordered sets do not allow duplicates and are initialized using comma-delimited values enclosed in curly braces.

Does set allow duplicates C++?

In Set duplicate values are not allowed to get stored. On other hand in case of MultiSet we can store duplicate values. In case of Set, one cannot change the value once it gets inserted however we can delete or insert it again. However in case of MultiSet also we cannot change the value once get inserted.

Which containers do not allow duplicates?

So, the conclusion, use std::unordered_set or std::unordered_map (if you need the key-value feature). And you don't need to check before doing the insertion, these are unique-key containers, they don't allow duplicates.