Validate Palindrome

Write a function that determines whether a given string is a valid palindrome. A palindrome is a word, phrase, or sequence that reads the same backward as forward. Ignore cases and all non-alphanumeric characters.

Input: A single string str.

Output: Return true if the string is a valid palindrome, false otherwise.

Example Inputs & Outputs

// Example 1:
Input: "A man, a plan, a canal: Panama"
Output: true

// Example 2:
Input: "race a car"
Output: false

// Example 3:
Input: " "
Output: true

// Example 4:
Input: "1234"
Output: false

// Example 5:
Input: "!!!@@@###"
Output: true. // ignores all the non alphanumeric characters

Constraints & Edge Cases

• The input string may contain letters, numbers, spaces, and special characters.
• Ignore cases (treat uppercase and lowercase the same).
• Ignore all non-alphanumeric characters.
• An empty string or a string with only non-alphanumeric characters is considered a valid palindrome.