All valid words that must have even number of a's or even number of b's [closed]

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All valid words that must have even number of a's or even number of b's

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I would recommend this site: http://rubular.com/. Its a sandbox for Regular Expressions where you can play around with them. It should help you solve your problem.

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You cannot do this with one regular expression. For one word you'd need to do something like

if ((replace(/[^Aa]/g, "").length & 1) == 0)

Of course this highly depends on your programming language (the above would work in JavaScript)