Is this a valid palindrome?

Focus on developing a clear and efficient algorithm to determine if a given string is a palindrome. Start by defining what constitutes a palindrome, considering both case sensitivity and non-alphanumeric characters. Discuss how you would handle edge cases, such as empty strings or strings with special characters. Be prepared to explain your thought process, including time and space complexity, and consider different approaches, such as using two pointers or reversing the string.