Find all directories that do not contain "main.cpp"
diff <(find . -exec readlink -f {} \; | sed 's/\(.*\)\/.*$/\1/' | sort | uniq) <(find . -name main.cpp  -exec readlink -f {} \; | sed 's/\(.*\)\/.*$/\1/' | sort | uniq) | sed -n 's/< \(.*\)/\1/p'