Regex for “Does not contain four or more repeated characters”

Question

My experience with regular expressions is limited and I\'ve been reading various tutorials and posts on negation and negative lookahead, etc, but nothing seems to quite matc

Answer 1

Turn the problem around: a character can be followed by at most 3 of the same. Then it must be followed by something else. Finally, the whole string must consist of sequences like this. In the perl flavor:

^((.)\2{0,3}(?!\2))*$