Regex for comma separated characters

Question

I'm looking for a regex to validate a set of non repeating characters separated by commas.

Given the set of characters like ABCD
Match any comma separated permutation (no repeating characters)
Some matches would be:
A
C
C,B
B,D
D,B,A,C
Some no matches would be:
A,A
ABC
D,B,A,B

This would work but doesn't allow the commas:

\b(?!(?:.\B)*(.)(?:\B.)*\1)[ABCD]+\b

what do you mean by "doesn't allow the commas"? you want to match it as a whole, including the commas? — Kristijan Iliev, Feb 18 '15 at 18:17

score 5 · Answer 1 · edited May 23 '17 at 12:12

5

Try if something like this would match your needs:

^(?:([A-D])(?!.*?\1),)*[A-D]$

If there's more than just one [A-D], preceding ones must be followed by a comma, captures prior [A-D] to \1 and checks if not followed by itself using a negative lookahead.

See test at regex101.com; Regex FAQ

edited May 23 '17 at 12:12

Community

1
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answered Feb 18 '15 at 18:22

Jonny 5

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Dunno why OP chose mine...Yours is more efficient :) – vks Feb 19 '15 at 12:50

score 2 · Accepted Answer · answered Feb 18 '15 at 18:29

2

^(?!.*?([A-D]).*?\1)[A-D](?:,[A-D])*$

Try this.See demo.

https://regex101.com/r/uC8uO6/8

answered Feb 18 '15 at 18:29

vks

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Nailed it. Complete and utter Rock and Roll! – jimatwork Feb 18 '15 at 20:11

Regex for comma separated characters

2 Answers2