I’m learning about question sentences.
I saw the example in my text book.
Where has Tom gone? -> Do you know where Tom has gone?
I understood it.
but if changes this sentences to “Do you know~”
Who saw you? -> Do you know who _____ ?
Is it correct that “Do you know who saw you?”
Your last sentence looks correct to me.
Thank you so much 
Recently caught overthinking it, still would a native go for smth like ‘Do you know who’s seen you\ Do you know who was seeing you’?
Hi Bangong,
Just to add - in your last sentence ‘who’ still remains the subject in ‘who saw you.’