Gives a set of regular expressions r_1, r_2, r_3, ..., r_n is there a regular expression which could be interpreted to say something similar to:

• match any permutation of r_1, r_2, r_3, ..., r_n
• match all of the following in any order: r_1, r_2, r_3, ..., r_n

The regular expression a|b|c...

• matches the letter a
• matches the letter b
• does not match the entire string cab. The regex will only align with exactly one letter from cab

For a given example, I could write down each and every permutation. The following is rather verbose:

ABC|BAC|CAB|ACB|BCA|CBA

CodePudding user response：

You can try the following:

^(?=[A-C]{3}$)(?!.*(.).*\1).*$

Here's a link to play around with it on regex101.com

CodePudding user response：

Use a combination of look aheads and length:

^(?=.*a)(?=.*b)(?=.*c).{3}$

This approach scales linearly, ie the regex has length O(n), when adding more terms, even though the permutations it matches grow factorially, ie O(n!)