LeetCode125 Valid Palindrome

很简单的题目

class Solution {
public:
    bool isPalindrome(string s) {
        if (s.empty()) return true; 
        int iSize = s.size();
        int i = 0;
        do 
        {
            if (!isalnum(s[i])) { i++; continue; }  
            if (!isalnum(s[iSize])) { iSize--; continue; }          
            if (tolower(s[i++]) != tolower(s[iSize--])) return false;
        }while(i