I unexpectedly met my friend.
My friend needs to go somewhere else, and has no time to chat.
What should I say to them?
Should I say "Hi!", because I just met them, or say "Bye!", because he's about to leave?
Honestly, those little meetings can be kind of frantic, it's perfectly OK to say something like:
"Hi, so good to see you... looks like you're busy though, so bye!"