Question

I’m experiencing some trouble ‘picking’ this data ‘apart’. Altough helper functions etc. are an option, I would really like to solve this using a regex only (and processing the matchgroups after matching).

This is (part of) the data I have:

Belgium
Belgium M_Foo
Belgium A_Bar
Belgium M_FooBar
Belgium S_Whooptee Doo
Belgium Xxx
Belgium S_Foo Bar
United Kingdom
United Kingdom W_Foo-Bar
United Kingdom M_Yay
United Kingdom Xxx
United Kingdom S_Derp
United Kingdom F_Doh Lorem
United Kingdom S_Ipsum Dolor
United States of America L_Foo
Macedonia F.Y.R. Xxx
Macedonia F.Y.R. S_Foo Bar
Cyprus (Greek) M_Foo
Congo (Democratic Republic of)
Congo (Democratic Republic of) Q_Yolo

Essentially this is a “key / value” sort of array of strings. It contains a countryname (which is not normalized so I can’t use hard-coded countrynames or ‘lookups’, it might as well be some other string than a countryname) and is optionally followed by either keyword Xxx or <random_upcase_char>_<random_text>.

I have come up with the following regex:

^(.+?)(?:\s+(Xxx|[A-Z]_.*)?)

or, small difference in the first matchgroup:

^(.*?)(?:\s+(Xxx|[A-Z]_.*)?)

This works fine for the first strings starting with Belgium. It returns, for these records, the following results:

Group 1     Group 2
================================
Belgium
Belgium     M_Foo
Belgium     A_Bar
Belgium     M_FooBar
Belgium     S_Whooptee Doo
Belgium     Xxx
Belgium     S_Foo Bar

However, the following lines cause trouble:

Group 1     Group 2
================================
United
United
United
United
United
United
United
United
Macedonia
Macedonia
Cyprus
Congo
Congo

What I’d like the regex to do is the following:

Group 1                         Group 2
================================================
United Kingdom
United Kingdom                  W_Foo-Bar
United Kingdom                  M_Yay
United Kingdom                  Xxx
United Kingdom                  S_Derp
United Kingdom                  F_Doh Lorem
United Kingdom                  S_Ipsum Dolor
United States of America        L_Foo
Macedonia F.Y.R.                Xxx
Macedonia F.Y.R.                S_Foo Bar
Cyprus (Greek)                  M_Foo
Congo (Democratic Republic of)
Congo (Democratic Republic of)  Q_Yolo

But I can’t get the first part to match. I’m pretty sure it has something to do with greedy/ungreedy options for the first matchgroup but after fiddling around for some time I can’t get it to work…

I don’t care if extra/other/more matchgroups are returned. The regex is intended to be used in a .Net C# application (in case you’re wondering which ‘dialect’ this is).

Any help would be very much appreciated.

Answer 1

Sometimes, with non-greedy matches, the anchoring is extremely important. In this case, anchoring to the end of the line solves the problem. Your regexp should be:

^(.+?)(?:\s+(Xxx|[A-Z]_.*))?$

Note that I also moved the optional (?) quantifier outside one more grouping level, so the space is optional.