【LeetCode】Valid Palindrome

class Solution {
public:
    bool isPalindrome(string s) {
        // IMPORTANT: Please reset any member data you declared, as
        // the same Solution instance will be reused for each test case.
        for(int i=0,j=s.length()-1;i<j;i++,j--)
        {
            while(i<j&&!((s[i]>='a'&&s[i]<='z')||(s[i]>='A'&&s[i]<='Z')||(s[i]>='0'&&s[i]<='9'))) i++;
            while(i<j&&!((s[j]>='a'&&s[j]<='z')||(s[j]>='A'&&s[j]<='Z')||(s[j]>='0'&&s[j]<='9'))) j--;

            if(i<j)
            {
                if(!(s[i]==s[j]||abs(s[i]-s[j])==abs('A'-'a'))) return false;
            }
        }
        return true;
    }
};