isPalindrome

Python

def is_palindrome(s):
  left, right = 0, len(s) - 1
  while left < right:
    while left < right and not s[left].isalnum():
      left += 1
    while left < right and not s[right].isalnum():
        right -= 1
    if s[left].lower() != s[right].lower():
      return False

    left += 1
    right -= 1

  return True
    

JavaScript

// O(n) time
// O(1) space
/**
 * @param {string} str
 * @return {boolean}
 */
export default function isStringPalindrome(str) {
  let leftIdx = 0;
  const result = str
    .replace(/[^a-zA-Z0-9]/g, '')
    .toLowerCase();
  let rightIdx = result.length - 1;
  while (leftIdx < rightIdx) {
    if (result[leftIdx] !== result[rightIdx]) {
      return false;
    }
    leftIdx++;
    rightIdx--;
  }
  return true;
}