Valid Palindrome
Difficulty: EasyTopic: Two PointersStringLeetcode:125.Valid PalindromeA 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 * 105sconsists only of printable ASCII characters.
Solution
write solution in here
/**
* @param {string} s
* @return {boolean}
*/
var isPalindrome = function (s) {
const isAn = (char) => {
let code = char.charCodeAt(0);
return (code >= 48 && code <= 57) || // 0-9
(code >= 65 && code <= 90) || // A-Z
(code >= 97 && code <= 122); // a-z
};
let l = 0, r = s.length - 1
while (l <= r) {
while (l < r && !isAn(s[l])) l++
while (l < r && !isAn(s[r])) r--
if (s[l].toLowerCase() !== s[r].toLowerCase()) {
return false
}
l++, r--
}
return true
};