From: Brian Candler <b.candler@...>
Date: 2009-06-01T17:44:59+09:00
Subject: Re: Regular expression

Mark Kremer wrote:
> I'm not sure if you still want the regex, but following regex should do
> the trick: ^(.{1})(?!\1)(.{1})(?!\1|\2).{1}\2$

Which is the same as the one I posted in my initial reply:

irb(main):009:0> /^(.)(?!\1)(.)(?!\1|\2)(.)(\2)$/ =~ "abcb"
=> 0
irb(main):010:0> /^(.)(?!\1)(.)(?!\1|\2)(.)(\2)$/ =~ "abbb"
=> nil
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