Should I write to him that I like him?

well if your so into righting a note, i think before ask do you have a gf either slip it in a late night texting or upfront or ask a friend or something, if he doesnt write a note saying, "you mean a lot to me, we have share the same idea and everything togethere, i hope we can be togethere when i come back" and leave a good photo of you smiling, i guess or write something else that if he doesnt have a gf that he wants you