125. Valid Palindrome.cpp

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