// Valid Palindrome
class Solution {
public:
  bool isPalindrome(string s) {
    int i = 0, j = 0;
    for (; i < s.size(); i++)
      if (isalnum(s[i]))
        s[j++] = s[i];
    for (i = 0; i < --j; i++)
      if (tolower(s[i]) != tolower(s[j]))
        return false;
    return true;
  }
};