#include <string>
#include <algorithm>
using namespace std;
 
bool isPalindrome(string s) {
    string cleaned;
    for (char c : s) {
        if (isalnum(c)) {
            cleaned += tolower(c);
        }
    }
    string rev = cleaned;
    reverse(rev.begin(), rev.end());
    return cleaned == rev;
}

def is_palindrome(s):
    cleaned = "".join(c.lower() for c in s if c.isalnum())
    return cleaned == cleaned[::-1]
 
print(is_palindrome("A man, a plan, a canal: Panama"))  # True

#include <string>
using namespace std;
 
bool isPalindrome(string s) {
    int left = 0, right = s.length() - 1;
 
    while (left < right) {
        // Skip non-alphanumeric from left
        while (left < right && !isalnum(s[left])) left++;
        // Skip non-alphanumeric from right
        while (left < right && !isalnum(s[right])) right--;
 
        if (tolower(s[left]) != tolower(s[right])) {
            return false;
        }
        left++;
        right--;
    }
    return true;
}

def is_palindrome(s):
    left, right = 0, len(s) - 1
 
    while left < right:
        # Skip non-alphanumeric from left
        while left < right and not s[left].isalnum():
            left += 1
        # Skip non-alphanumeric from right
        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
 
print(is_palindrome("A man, a plan, a canal: Panama"))  # True
print(is_palindrome("race a car"))                       # False

class Solution {
    public boolean isPalindrome(String s) {
        int left = 0, right = s.length() - 1;
 
        while (left < right) {
            while (left < right && !Character.isLetterOrDigit(s.charAt(left)))
                left++;
            while (left < right && !Character.isLetterOrDigit(s.charAt(right)))
                right--;
 
            if (Character.toLowerCase(s.charAt(left)) !=
                Character.toLowerCase(s.charAt(right))) {
                return false;
            }
            left++;
            right--;
        }
        return true;
    }
}