How to check whether string is palindrome or not using regular expression

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Hi ,

I am writing console application which will check for word whether it is Palindrome or not. But i dont know how to do it using regular expression can you please suggest for the same. also wanted to ignore none-alphanumeric characters.

Eg. Mad&**am is a palindrome

Thanks

What I have tried:

static void Main(string[] args)
{
string s, revs = "";
Console.WriteLine(" Please Enter a string value");
s = Console.ReadLine();
for (int i = s.Length - 1; i >= 0; i--)
{
revs += s[i].ToString();
}
//string checking for pallindrome
if (revs == s)
{
Console.WriteLine("String is Palindrome \n Entered String Was {0} and reverse string is {1}", s, revs);
}
else
{
Console.WriteLine("String is not Palindrome \n Entered String Was {0} and reverse string is {1}", s, revs);
}
Console.ReadKey();
}

Posted 17-Jun-16 23:33pm

Torakami

Updated 17-Jun-16 23:53pm

v3

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OriginalGriff · Answer 1 · 2016-06-17T23:53:00

Solution 1

Don't even try.
A regex is definitely the wrong tool for that. You could do it, but it'd be horrible.
Instead, just do it in C# code.
By a total coincidence, I wrote this yesterday for someone else:

C#

private static bool IsPalindrome(string inputString)
    {
    char[] inputArray = inputString.ToLowerInvariant().Where(char.IsLetter).ToArray();
    int len = inputArray.Length;
    for (int i = 0; i < len / 2; i++)
        {
        if (inputArray[i] != inputArray[len - (i + 1)]) return false;
        }
    return true;
    }

Posted 17-Jun-16 23:53pm

OriginalGriff

Comments

Torakami 18-Jun-16 6:31am

Thanks for answer , but can you explain me why not to go for regex ?

OriginalGriff 18-Jun-16 6:48am

Because regexes are text processors, they don't include any logical operations. So they can return a "match / didn't match" result, but they really aren't good at "ignore all characters except these types, and then match them up in pairs (unless it's the center one of the non-matched characters if there are an odd number of those)" type decisions. So while it can be done, the actual regex would be horrible, both the look at, to understand, and to modify. If you want to go for it, then do:
http://www.ultrapico.com/Expresso.htm
will help you, but I seriously wouldn't recommend it. It will take quite a lot of time and effort to get it working.
Just because something is possible, doesn't mean you should do it! :laugh: