leetcode/work/Easy/Two Pointers/125.valid-palindrome.js

/*
 * 125. Valid Palindrome
 * Difficulty: Easy
 * https://leetcode.com/problems/valid-palindrome/
 * 
 * ──────────────────────────────────────────────────
 * 
 * A phrase is a palindrome if, after converting all uppercase letters
 * into lowercase letters and removing all non-alphanumeric characters,
 * it reads the same forward and backward. Alphanumeric characters
 * include letters and numbers.
 * 
 * Given a string s, return true if it is a palindrome, or false
 * otherwise.
 * 
 *  
 * 
 * Example 1:
 * 
 * Input: s = "A man, a plan, a canal: Panama"
 * Output: true
 * Explanation: "amanaplanacanalpanama" is a palindrome.
 * 
 * Example 2:
 * 
 * Input: s = "race a car"
 * Output: false
 * Explanation: "raceacar" is not a palindrome.
 * 
 * Example 3:
 * 
 * Input: s = " "
 * Output: true
 * Explanation: s is an empty string "" after removing non-alphanumeric
 * characters.
 * Since an empty string reads the same forward and backward, it is a
 * palindrome.
 * 
 *  
 * 
 * Constraints:
 * 
 * 	• 1 <= s.length <= 2 * 10^5
 * 
 * 	• s consists only of printable ASCII characters.
*/

/**
 * @param {string} s
 * @return {boolean}
 */
var isPalindrome = function(s) {
  let normal = s.replace(/[^a-zA-Z0-9]/g, "").toLowerCase()    
  let i = 0, j = normal.length - 1;

  while (i < j) {
    if(normal[i] !== normal[j]) {
      return false;
    }
    i++;
    j--;
  }
  return true;
};