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Problem: Valid Palindrome

Understand how to determine if a string is a palindrome by converting characters to lowercase and skipping non-alphanumeric ones. Learn to implement a two-pointer approach that compares characters from the ends inward, achieving linear time and constant space complexity.

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:

  • 11 \leq s.length 2×105\leq 2 \times 10^5 ...