This is the contents of the directory I\'m working with:
misha@hp-laptop:~/work/c/5$ ls -l total 8 -rw-rw-r-- 1 misha misha 219 May 20 15:37 demo.c drwxrwxr
You can change your find command to this:
find
find . -mindepth 1 -not -name demo.c -delete
-mindepth 1
DOT
-delete