Is a Palindrome String?

Problem

Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.

Example

Input : "Red rum, sir, is murder" is a palindrome, while"
Output: true

Input : "Ahmed is Engineer"
Output: false

Input : ""
Output: true

Input : "a"
Output: true

Analysis

A usual palindrome problem is a little easier, since the assumption is all sort of charachters are included, for instance “abba” is a simple palindrome. we can use two indcies to traverse forward and backward and compare values for matching, an algorithm of time compliexity O(n/2)

    public static bool IsPalindrome(string str)
    {
        if (string.IsNullOrEmpty(str) || str.Length == 1)
            return true;

        int i = 0; int j = str.Length - 1;
        while(i < j)
        {
            if (str[i++] != str[j--]) return false;
        }


        return true;
    }

But in this case we want to only consider alphanumeric characters and ignoring cases , we still run a forward and backward traverse , for each charachter we will check is letter is letter or digit using framework helper methdo Char.IsLetterOrDigit() , if not then we move get next charachter until we get an alphanumeric char.

CSharp Solution

Happy Coding!