Question

Assume the following strings:

• A01B100
• A01.B100
• A01
• A01............................B100 ( whatever between A and B )

The thing is, the numbers should be \d+, and in all of the strings A will always be present, while B may not. A will always be followed by one or more digits, and so will B, if present. What regex could I use to capture A and B’s digit?

I have the following regex:

(A(\d+)).*?(B?(\d+)?)

but this only works for the first and the third case.

Answer 1

• Must A precede B? Assuming yes.
• Can B appear more than once? Assuming no.
• Can B appear except as part of a B-number group? Assuming no.

Then,

A\d+.*?(B\d+)?

using the lazy .*? or

A\d+[^B]*(B\d+)?

which is more efficient but requires that B be a single character.

EDIT: Upon further reflection, I have parenthesized the patterns in a less-than-perfect way. The following patterns should require fewer assumptions:

A\d+(.*?B\d+)?
a\d+([^B]*B\d+)?