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I need a regex that matches a string with the following specifications:
> At least one alpha-numeric character, followed by one or zero '?' or one or zero '!', but does not contain both '?' and '!'. Examples of valid strings: 'xyz', 'zy!', 'Xy?'
I have come up with this so far, which does not work:
[0-9]|[a-z] + ?! + ?? ^[^<>]+$
One option could be repeating a character class [A-Za-z0-9]+ 1+ times followed by matching an optional question or exclamation mark using another character class [?!]?
To prevent being part of a larger word you might start the pattern with a wordboundary \b and end asserting (?!\S) not a non whitespace char on the right.
\b[A-Za-z0-9]+[?!]?(?!\S)
To match the exact string only you might use anchors ^ to assert the start and $ end of the string.
^[A-Za-z0-9]+[?!]?$
