Kata

Implement a function that determines whether a string is a palindrome. A palindrome is a sequence of characters that reads the same backward or forward.

Assume that the empty string is a palindrome. Any character in a nonempty input string that is not alphanumeric (use the isAlphaNum function) will be ignored. Letter case is ignored as well.

Examples of input strings that produce a result of True:

• "Star rats"
• "elite ti le"
• "noon"
• "Poor Dan is...in a droop!"
• "89#8"
• " dffd " (notice the leading and trailing whitespaces)

Note: Unlike another palindrome kata, this kata doesn't forbid the use of standard language functions that reverse a list.