Problem Statement

Given a string s, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.

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.

Constraints:

• 1 <= s.length <= 2 * 105
• s consists only of printable ASCII characters.

Problem Link

Valid Palindrome - LeetCode

Code

class Solution {
public:
    bool isPalindrome(string s) {
        
       int n = s.size();
        
       int start = 0;
        int end = n-1;
        
       while(start<end)
       {
           while(start<end&&!isalnum(s[start]))
               start++;
           
           while(start<end&&!isalnum(s[end]))
               end--;
           
           if(tolower(s[start])!=tolower(s[end]))
               return false;
           start++;
           end--;
       }
        
        return true;
           
           
        
       
        
    }
};