Issue with regular expressions in C++

Question

I tried to use the following regular expression, which already works in C#, in C++ as well but it\'s not working in C++.

Answer 1

This is similar sln's, but it's shorter and doesn't require a % part to match:

^(?:[^%]*(?:%\.?[0-9]*[a-z])?)*$

First - everything between ^ (start of line) and $ (end of line) is optional, so an empty string is accepted.

In an optional, non capturing group (?:...), match any number of anything but a %. Then, optionally, match a %, optionally followed by a ., and then any number of digits and finally a letter. Repeat this for any number of times.

(I, as the others answering, and as the regex provided in the question suggests, assume that OP doesn't mean "immediately preceded by a letter", but instead followed by one, right?)

See it here at regex101.