[LeetCode] Valid Palindrome

Given a string, determine if it is a palindrome, considering only alphanumeric(字母与数字) characters and ignoring cases.

For example,
"A man, a plan, a canal: Panama" is a palindrome.（不区分大小写）
"race a car" is not a palindrome.

Note:
Have you consider that the string might be empty? This is a good question to ask during an interview.

For the purpose of this problem, we define empty string as valid palindrome.

Solution:

class Solution {
public:
    bool isPalindrome(string s) {
        string ss = "";
        for(int i = 0;i < s.length();i++)
        {
          if(s[i] >= 'A' && s[i] <= 'Z')
            ss += s[i] - 'A' + 'a';
          else if(s[i] >= 'a' && s[i] <= 'z')
            ss += s[i];
            else if(s[i] >= '0' && s[i] <= '9')
                ss += s[i];
        }

        if(ss.length() < 2)
          return true;
        else
        {
          for(int i = 0;i < ss.length() / 2;i++)
          {
            if(ss[i] != ss[ss.length() - 1 - i])
              return false;
          }
          return true;
        }
    }

};