Regular Expression For Finding Palindromes Behaving Strange

I want to write a program which finds palindromes (words which are the same from start to end and end to start like anna). But it should also work for multiple words car a rac and

Solution 1:

Your regular expression cannot match overlapping regions (you'd need to play with look-arounds with capturing groups to do that).

The expression matches the first three x characters first; it matches:

• one character (group 1), zero spaces (group 2), an optional character (the ? is greedy), the zero spaces from group 2, the one character from group 1.

The second match then has to start after that; the two xx characters match because the [a-z]? pattern is optional.

You cannot create a regular expression to match palindromes in general (at least not with the Python re engine), as there is no facility to match an arbitrary-width previous group in reverse.