How to replace a letter 'b' to 'c' after a duplicate letter 'a' base on 2 times? for example :
ab => ab
aab => aac
aaab => aaab
aaaab => aaaac
aaaabaaabaab => aaacaabaac
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The last example doesn't match in the number of characters (?)Sebastián Palma– Sebastián Palma2017-05-13 14:51:50 +00:00Commented May 13, 2017 at 14:51
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1@SebastiánPalma: I think it's a typo on OP's behalf.Rahul– Rahul2017-05-13 15:05:05 +00:00Commented May 13, 2017 at 15:05
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1 Answer
You should check groups of aa followed by b and then replace captured groups accordingly.
Regex: (?<!a)((?:a{2})+)b
Explanation:
(?<!a) checks for presence of an odd numbered a. If present whole match fails.
((?:a{2})+)b captures an even number of a followed by b. Outer group is captured and numbered as \1.
Replacement: \1c i.e first captured group followed by c.
Test String:
ab
aab
aaab
aaaab
aaaabaaabaab
After replacement:
ab
aac
aaab
aaaac
aaaacaaabaac
