題目：Determine whether an integer is a palindrome. Do this without extra space.

Some hints:

Could negative integers be palindromes? (ie, -1)

If you are thinking of converting the integer to string, note the restriction of using extra space.

You could also try reversing an integer. However, if you have solved the problem "Reverse Integer", you know that the reversed integer might overflow. How would you handle such case?

There is a more generic way of solving this problem.

bool isPalindrome(int x) 
    {
        //如果x<0，則返回錯誤
        if(x < 0)
        return false;
        
        int d = 1;  //除數
        
        //求出首次要除的除數
        while (x / d >= 10) 
            d *= 10;
        while (x > 0) 
        {
            int q = x / d;  // x的首位數
            int r = x % 10; // x的末位數
            if (q != r) 
                return false;
            x = x % d / 10; //x為去掉首位和末位
            d /= 100;   //除數/100,繼續判斷
        }
        return true;
    }