Leetcode#125 Valid Palindrome

 1 bool isPalindrome(string s) {
 2         string news;
 3         for (auto c : s)
 4             if (isalnum(c))
 5                 news += tolower(c);
 6         
 7         int i = 0;
 8         int j = news.length() - 1;
 9         while (i < j && news[i] == news[j]) {
10             i++;
11             j--;
12         }
13         
14         return i >= j;
15 }