How to sort the results of `find` alphabetically and topologically?

Let's say I have the following files laid out like this:

$ tree
.
├── 01/
│   ├── example.txt
│   └── foobar.txt
├── 02/
│   └── example.txt
└── 03/
    ├── example.txt
    └── test.txt

3 directories, 5 files

I would like find . to print out the directories and files in order, topologically (that is directory names before their contents), and within the same directory, alphabetically. Instead, these are the results I get:

$ find .
.
./02
./02/example.txt
./01
./01/foobar.txt
./01/example.txt
./03
./03/test.txt
./03/example.txt

I would like the output to look like:

.
./01
./01/foobar.txt
./01/example.txt
./02
./02/example.txt
./03
./03/example.txt
./03/test.txt

I don't want to pipe to sort or to any other command, because I would like to process the lines one by one in order before the find command completes.