Question

I would like to validate a string for letters A-Z, AA-ZZ, AAA-ZZZ, and so on with a regex. I know [A-Z] will validate the first case but what about the others.

A, B, C, D, E, .... Z

or

AA, BB, CC, DD, EE, .... ZZ

or

AAA, BBB, CCC, DDD, EEE, ... ZZZ

and so on…

Answer 1

You can use backreference, if your regex engine supports it:

^([A-Z])\1*$