Valid Palindrome

Given a string, implement a function to check if it is a palindrome string. Only alphanumeric characters should be considered and case is ignored. For example, "A man, a plan, a canal: Panama" is a palindrome while "race a car" is not. Input A string s with length in the range [0, 2 * 10^5]. Output Return true if s is a palindrome string, otherwise return false. Example Example 1: Input: "A man, a plan, a canal: Panama" Output: true Example 2: Input: "race a car" Output: false Example Input "A man, a plan, a canal: Panama"