Problem: Valid Palindrome
Explore how to verify if a string is a valid palindrome after normalizing case and filtering non-alphanumeric characters. Learn to implement an efficient two-pointer approach in C# that compares characters from both ends without extra space, ensuring linear time complexity and constant space usage.
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Statement
A phrase is considered a palindrome if, after converting all uppercase letters to lowercase and stripping all non-alphanumeric characters, it reads the same forward and backward. Alphanumeric characters include both letters and numbers.
Given a string s, return true if it qualifies as a palindrome after the transformations described above, or false otherwise.
Note: An empty string (which may result after removing all non-alphanumeric characters) is considered a palindrome.
Constraints:
s.Length...