When two people meet, and one of them says hello but the other one can't recognize him or her, the other one would ask "Do I know you?"
I know this is natural for English speakers but it could be strange for some non native speakers like me.
Because in this situation I would ask "Do you know me?"
Why do English speakers ask in this way?
From a common-sense standpoint, it is strange to ask others whether I know someone or not.