Using the following regex
^(\d)(?!\1+$)\d{3}-\d{1}$
It works for the pattern but I need to validate that all numbers are not the same even after /separated by the hyphen (-).
Example:
0000-0 not allowed (because of all are same digits)
0000-1 allowed
1111-1 not allowed (because of all are same digits)
1234-2 allowed
You could exclude only - or the same digit only to the right till the end of the string:
^(\d)(?!(?:\1|-)*$)\d{3}-\d$
^ Start of string(\d) Capture group 1, match a digit(?! Negative lookahead, assert what is to the right is not
(?:\1|-)*$ Optionally repeat either the backrefernce to what is already captured or - till the end of the string) Close the non capture group\d{3}-\d Match 3 digits - and a digit$ End of stringIf you don't want to match double -- or an - at the end of the string and match optional repetitions:
^(\d)(?!(?:\1|-)*$)\d*(?:-\d+)*$
Explanation
^ Start of string(\d) Capture a single digits in group 1(?!(?:\1|-)*$) Negative lookahead, assert not only - and the same digit till the end of the string\d* Match optional digits(?:-\d+)* Optionally repeat matching - and 1+ digits$ End of stringTheFourthBird's answer surely works that uses a negative lookahead. Here is another variant of this regex that might be slightly faster:
^(\d)(?!\1{3}-\1$)\d{3}-\d$
Explanation:
^(\d) matches and captures first digit after start in group #1(?!\1{3}-\1$) is a negative lookahead that will fail the match if we have 3 repetitions and a hyphen and another repeat of 1st digit.