Regex: I want this AND that AND that… in any order

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You can use (?=…) positive lookahead; it asserts that a given pattern can be matched. You’d anchor at the beginning of the string, and one by one, in any order, look for a match of each of your patterns.

It’ll look something like this:

^(?=.*one)(?=.*two)(?=.*three).*$

This will match a string that contains "one", "two", "three", in any order (as seen on rubular.com).

Depending on the context, you may want to anchor on \A and \Z, and use single-line mode so the dot matches everything.

This is not the most efficient solution to the problem. The best solution would be to parse out the words in your input and putting it into an efficient set representation, etc.

Related questions

More practical example: password validation

Let’s say that we want our password to:

  • Contain between 8 and 15 characters
  • Must contain an uppercase letter
  • Must contain a lowercase letter
  • Must contain a digit
  • Must contain one of special symbols

Then we can write a regex like this:

^(?=.{8,15}$)(?=.*[A-Z])(?=.*[a-z])(?=.*[0-9])(?=.*[!@#$%^&*]).*$
 \__________/\_________/\_________/\_________/\______________/
    length      upper      lower      digit        symbol

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