Be careful. A user needs execute permission on a directory to pass through, read permission to view contents. opendir will succeed on a directory where you have '--x' permissions but you will obviously not have access to directory contents. Make sure a component of your solution actually tries a read on each directory.

Update:

I was not clear, opendir will fail on a directory that doesn't have it's 'r' bit set (assuming non-root). However if I open a directory say /homes/insensate/allx/freeforallWhere  allx is  --x--x--x and freeforall is  rwxrwxrwx the opendir will succeed.

My point is to not let an assumption that access to a given directory implies access to parent directories stand.