RegEx / computer theory - construct a regEx in alphabetical order

Question

In my grammars - Computer theory class I am trying to create a regular expression in alphabetical order(az)

l = {a, b, x, y, z, i, o, u, e, c}

This is what i have come up with using the kleene closure

aeiou(x*, y*, z*, i*, o*, u* e*) 

With the kleene close * thats zero or more so that should force abceioxyz?

We have not been learning this type of form

[^abc]

am i on the right track?

Answer 1

As far as I understand, you want to capture strings with the following format:

• The string contains any number of a 's, afterwards any number of b 's, then any number of c 's, and so on...

Let's consider a derived example: We want all strings consisting of 0 and 1 and that has all 0 's before 1 's: Therefore, we can simply write 0*1* . Now try to adapt the pattern for more complex alphabets.

Answer 2

the word must be in alphabetical order, so if it contains any a's, they surely must be at the front. likewise, if it contains any b's , they must come after the a's, and nothing can come in between the a's and b's

so we have: a*b*...

and so a pattern emerges.