Finding empty directories
It depends a little on what you want to do with the empty directories. I use the command below when I wish to delete all empty directories within a tree, say test directory.
find test -depth -empty -deleteOne thing to notice about the command above is that it will also remove empty files, so use the -type d option to avoid that.
find test -depth -type d -empty -deleteDrop -delete to see the files and directories matched.
If your definition of an empty directory tree is that it contains no files then you be able to stick something together based on whether find test -type f returns anything.
find is a great utility, and RTFM early and often to really understand how much it can do :-)