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[LeetCode 125] Valid Palindrome
Problem
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 * 105
- s consists only of printable ASCII characters.
TypeScript
function isPalindrome(s: string): boolean {
s = s.toLowerCase().split('').filter(c => ('a' <= c && c <= 'z') || ('0' <= c && c <= '9')).join('')
if (s.length <= 1) return true;
let left: number = 0, right = s.length - 1;
while(left < right){
if(s[left] !== s[right]) return false;
left++;
right--;
}
return true;
};