Question

I have a vector with different values and some of them may appear twice. (Only twice.)
How can I find the FIRST duplicate item?

Like: [a][b][b][a]
Then I’d need ‘b’.

(Sorry for the newbie question.)

Answer 1

If you’re looking for adjacent duplicates, you can simply use std::adjacent_find.

If the duplicates aren’t necessarily adjacent, then you could first std::sort the vector, and then use std::adjacent_find on the result. (See @aix’s comment below)

Alternatively, you could push each element into a std::set, and look for collisions as you’re doing it.