What's a Regex pattern for 3 consecutive digits increasing or decreasing.

Question

I need a regex pattern to match a sequence of 3 consecutive digits in a string that are consecutively increasing or decreasing.

For example:

These strings should match (xxx123xxx, 789xxxxxx, xxxxxx987, xxxxxx432)

These strings should not match (xxxxxx454, 333xxxxxx, xxx429xxx)

Answer 1

There is no other way than listing them:

(012|123|234|345|456|567|678|789|987|876|765|654|543|432|321|210)

Answer 2

This is going to be a very complicated regex. On a project where I had to do something very similar, I ended up matching digit groups and then passing off the actual validation of the digits to a delegate (I was doing this in C++ code; have done something similar on another project in Java in the same way).

If at all possible, this is what I'd recommend doing here. A regex which could do this all by itself would be very difficult to read or maintain.

Answer 3

This can be done simply, but only with defining the valid sets of consecutive digits

(?:012|210|123|321|234|432|345|543|456|654|567|765|678|876|789|987)